B13 - Reproduction (Y11 Spring 1)

Question 1

🟢 What way does Sexual Reproduction work and what does it result in?

Answer 1

It works with 2 different sex cells meeting and fusing with each other.

This is called sexual reproduction and results in Genetic Diversity

Question 2

🟢 What way does Asexual Reproduction work and what makes it Asexual

Answer 2

It works by one parent undergoing a type of cell division which produces genetically identical cells in the new organism.

Since sex cells are not involved this is called asexual reproduction.

Question 3

🟢 How are Gametes formed?

Answer 3

Gametes are formed through Meiosis, where sperm (male gamete) is formed in the testes and eggs (female gametes) are formed in the ovary.

Question 4

🟢 How are Genes are Characteristics passed on in Asexual Reproduction?

Answer 4

In asexual reproduction, offspring have all the same genes and characteristics as the one parent.

Question 5

🟢 How are Genes are Characteristics passed on in Sexual Reproduction?

Answer 5

In sexual reproduction, offspring have a mixture of genes and characteristics from two parents or two gametes.

Question 6

🟢 What is Reproduction and What are the Two Types

Answer 6

During reproduction, genetic information in the chromosomes is passed on from parents to their offspring. There are two different ways of reproducing - asexual reproduction, and sexual reproduction.

Question 7

🟢 What is Asexual Reproduction And What Happens In It

Answer 7

Asexual reproduction only involves one parent. The cells divide by mitosis. There is no joining (fusion) of special sex cells (gametes) and so there is no mixing of genetic information. As a result, there is no variation in the offspring. Asexual reproduction gives rise to genetically identical offspring known as clones. Their genetic material is identical both to the parent and to each other. Only mitosis is involved in asexual reproduction.

Question 8

🟢 What Organisms/Things Use Asexual Reproduction

Answer 8

Asexual reproduction is very common in the smallest animals and plants, and in fungi and bacteria. Also many larger plants like daffodils, stawberries, and brambles reproduce asexually. The cells of our bodies also reproduce asexually, as they divide into two identical cells for growth and to replace worn out cells.

Question 9

🟢 What is Sexual Reproduction And What Happens In It

Answer 9

Sexual reproduction involves a male sex cell and a female sex cell from two parents. These two gametes fuse together to form a zygote which goes on to develop a new individual. Gametes are formed in a special form of cell divison called meiosis.

Question 10

🟢 How Does Asexual Reproduction Result In Variation

Answer 10

The offspring that result from sexual reproduction inherit genetic information from both parents. They will have some characteristics from both parents. They will have some characteristics from both paremts, but won’t be identical to either of them. This introduces variation. The offspring of sexual reproduction show much more variation than the offspring from asexual reproduction.

Question 11

🟢 What Organisms Use Sexual Reproduction (What Gametes are used in Plants and Animals)

Answer 11

Sexual reproduction involves the joining (fusion) of male and female gametes:

• sperm and egg cells in animals
• pollen and egg cells in flowering plants

Question 12

❌ Advantages of Asexual Reproduction

Answer 12

• If a parent has desirable charactristics, they are passed on to the offspring
• It’s quicker than sexual reproduction
• No mates are needed to reproduce

Question 13

❌ Disadvantages of Asexual Reproduction

Answer 13

• There is no genetic diversity, therefore single strains are more susceptible to the same diseases
• If there are too many indentical offspring, then they will compete against each other
• If the parent has undesirable characteristics, those are also passed on

Question 14

❌ Advantages of Taking Cuttings:

Answer 14

• It’s quick
• It’s cheap
• It’s easy
• It’s rapid (you can make many new plants)

Question 15

❌ *What Things Can Be Done With Asexual Reproduction

Answer 15

In asexual reproduction, it can:

• inlcude cloning
• include natural clones
• involve mitosis
• taking a tissue culture (taking cuttings)

Question 16

❌ Advantages Of Sexual Reproduction

Answer 16

• Produces variation in the offspring (key to the long-term survival of a species)
• If the environment changes variation gives a survival advantage by natural selection
• Natural selection can be speeded up by humans in selective breeding to increase food production.

Question 17

❌ Disadvantages Of Sexual Reproduction

Answer 17

• Desirable characteristics from a parent will not always be passed on
• A mate is needed to reproduce
• It can be risky as it relies on two gametes fusing and can take longer for a species to reproduce as a result.

Question 18

🟢 What Is Meiosis/What Does Meiosis Result In (What Are Male+Female Gametes)

Answer 18

Meiosis results in sex cells called gametes, which have only half the original number of chromosomes. Female gametes are egg cells/ova which are made in the ovaries. The male gametes are sperm and are made in the tested.

Each gamete has 23 chromosomes, so when they combine, a full 46 chromosomes needed for a human a made.

Question 19

🟢 What Happens in Meisosis

Answer 19

Cells in reproductive organs divide by meiosis to form gametes.

When a cell divides to form gametes:

• Copies of the genetic information are made
• The cell divides twice to form four gametes, each with a single set of chromosomes

Each gamete produced is genetically different from all the others. Gametes contin random mixtures of the original chromosomes. This introduces variation.

Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo develops cells differentiate.

Question 20

🟢 *Full Sequence of What Happens In Meiosis

Answer 20

1. In humans, there are 46 chromosomes (23 pairs). One chromosome in each pair comes from the mother and father. Each chromosome in the pair is equal in length.
2. A copy is made of each chromosome. The original and the copy stay together.
3. The chromosome pairs line up down the centre of the cell. The pair from the father matches up with the corresponding pair from the mother.
4. The chromosome pairs separate and move to opposite ends of the cell (like mitotic division resulting in 23 pairs of chromosomes in each new nucleus)
5. The chromosome paors now line up again in preparation for a second division.
   The second division separates each original chromosome from its copy so that eqch new cell has 23 chromosomes.
   The new cell that form are called gametes.
6. Four new Haploid cells are for ed each containing 23 chromosomes. Each sex cell (sperm/egg) has a unique set of genes.
7. The sperm swims to the ovum and the head enters. The two nuclei merge to produce a fertilised efg containing 46 chromosome that can grow by mitotic division to form an embryo.

Question 21

🟢 How Is More Variation Added in Fertilisation?

Answer 21

Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo develops cells differentiate into tissue, organs, and organ systems e.c.t.

Question 22

🟢 Why is there no Variation in Asexual Reproduction

Answer 22

In asexual reproduction, the offspring are produced as a result of mitosis from the parent cells. They contain exactly the same chromosomes and the same genes as their parents. There is no variation in the genetic material

Question 23

🟢 Why is there Variation in Sexual Reproduction

Answer 23

In secual reproduction, the gametes are produced by meisosis in the sex organs of the paremts. This introduces variation as each gamete is different. Then, when gametes fuse, one of each pair of chromosomes, and so one of each pair of genes comes from each parent, adding more variation. The combination of genes in the new pair of chromosomes will contain different forms of the same genes (alleles) from each parent. This also helps to produce variation in the characteristics of the offspring.

Question 24

🟢 What Do Fungi Reproduce Sexually and Asexually For

Answer 24

Many fungi reproduce asexually by spores but also reproduce sexually to give variation.

Question 25

🟢 What Do Plants Reproduce Sexually and Asexually For

Answer 25

Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils.

Question 26

🟢 What Do Malarial Paresites Reproduce Sexually and Asexually For

Answer 26

Malarial parasites reproduce asexually in the human host, but sexually in the mosquito.

Question 27

❌ Advantages For Fungi Reproducing Both Sexually and Asexually

Answer 27

• Moulds that rot our food reproduce asexually as it’s faster and more efficient
• Some fungi reproduce sexually when conditions are not good, e.g if it’s dry

-Some spores produced from two different hyphae may be better
adapted to survive in more adverse conditions

Question 28

❌ Disadvantages For Fungi Reproducing Both Sexually and Asexually

Answer 28

-Some fungi reproduced sexually may not have as many good characteristics in some cases

Question 29

❌ Advantages For Plants Reproducing Both Sexually and Asexually

Answer 29

• Sexual reproduction in plants introduce variation and enables the plant to survive as conditions chamge throughout natural selection
• Asexual reproduction, as a result of specialy directed mitosis, is how a new plant grows
• With asexual reproduction, new plants are formed even if flowers are destroyed by frost, eaten, or fail to be pollinated.

Question 30

❌ Disadvantages For Plants Reproducing Both Sexually and Asexually

Answer 30

• New plants are identical to their parents and no variation is introduced.
• Some desirable charcateristics may be lost through pollinating plants sexually reproducing

Question 31

❌ Advantages For Plants Reproducing Both Sexually and Asexually

Answer 31

-Malarial parasites reproduce asexually in human
liver and blood cells

-When the mosquito takes her blood meal, the
drop in temperature between the human body and
the mosquito triggers sexual reproduction in some
of the parasites inside the red blood cells. There is a
20 minute window where sexual forms develop

• These zygotes undergo meiosis to produce new asexual parasites that will infect a human host
• The parasites show a lot of variation

Question 32

❌ Disadvantages For Plants Reproducing Both Sexually and Asexually

Answer 32

-Asexual reproduction is not an alternative only if conditions are bad

Question 33

🟢 What is the Genetic Material composed of

Answer 33

The genetic material in the nucleus of a cell is composed of a chemical called DNA.

Question 34

🟢 What do your Chromosomes contain?

Answer 34

Each of your chromosomes contains thousands of genes joined together

Question 35

🟢 What is DNA

Answer 35

DNA is a polymer made up of two strands (double stranded molecule) forming a double helix. The DNA is contained in structures called chromosomes. Bases are paired in the middle, and the four bases combine by complementary base pairings.

Question 36

🟢 What are Genes

Answer 36

A gene is a small section of DNA on a chromosome. Each gene codes for a particular sequence of amino acids, to make a specific protein. (Genes are what control your characteristics)

Question 37

🟢 What is the Genome of an Organism

Answer 37

The genome of an organism is the entire genetic material of that organism. The whole human genome has now been studied and this will have great importance for medicine in the future.

Question 38

🟢 What is the Relationship between Genes and the whole Organism (+What do Genes Control)

Answer 38

Each gene codes for a particular sequence of amino acids, to make a specific protein. These proteins include enzymes that control your cell chemistry. This is how the relationship between genes and the whole organism builds up. The genes control the proteins, which control the make up of the different specialised cells that form tissues. These tissues then form organs and organ systems that make up the whole body.

Question 39

🟢 When did Scientists announced they had sequenced the Human genome and how

Answer 39

In 2003, scientists announced that they had managed to sequence the human genome. Working in teams all around the world, the Human Genome project finished two years early, and under budget too. This was because the technology used to chop up the DNA and read all the base sequences had improved so fast during the life of the project.

Question 40

🟢 What is the Genome of an Organism?

Answer 40

The genome of an organism is the entire genetic material of the organism. That includes all of the chromosomes, and the genetic material found in the mitochondria as well. Mitochondria contain their own DNA. You always inherit your mitochondria DNA from your mother because it comes from the mitochondria in the egg.

Question 41

🟢 What is the Human Genome made up of?

Answer 41

The human genome contains over 3 billion base pairs and almost 21,000 genes that code for proteins. That sounds a lot until you discover that rice has 36,000 coding genes. We are not simpler than rice. The human genome has the ability to make many different proteins from the same gene by using it in different ways, or by switching part of a gene on or off.

Question 42

🟢 How have the Human Genome projects numbers Increased since the Initial Genome was read

Answer 42

Since the initial genome was read, scientists have carried on with the work. They went on to sequence the genomes of 1000 people, and now they are busy with 10,000 genomes project. The aim js to find out as much as possible about human DNA.

Question 43

🟢 Why are Scientists sequencing other Genomes

Answer 43

It isn’t just human genomes that are sequenced. Scientists are sequencing the genomes of hundreds of different species of organisms. They use similarities and differences in the genomes to help them work out the relationships between different types of organisms. It is changing the way we classify living things. Sequencing the genomes of bacteria and vieuses allows us to identify the causes of disease very rapidly and to choose correct treatment.

Question 44

🟢 Why is Understanding the Human Genome Important? (What can it help us understand)

Answer 44

Understanding the human genome can help us understand many things including:

• Inherited Disorders
• Finding Genes That Link To Different Types Of Diseases
• Finding Cancer Treatments
• Human Evolution and History

Question 45

🟢 How does Understanding the Human Genome help with Inherited Disorders

Answer 45

It will help inherited disorders such as cystic fibrosis and sickle cell disease. The more we can understand what goes wrong in these dieases, the more chance we have in overcoming them either through medicines or by repairing faulty genes.

Question 46

🟢 How does Understanding the Human Genome help with Finding Genes That Link To Different Types Of Diseases

Answer 46

There are genes that are linked to increased risk to developing many diseases, from heat disease to type 2 diabetes. Understanding the human genome is playing a massive part in the search for genes linked to different types of diseases. The more we understand about the genome, the more likely we are to predict the risk for each person

Question 47

🟢 How does Understanding the Human Genome help with Finding Cancer Treatments

Answer 47

The more we understand about the genome, the more likely we are to predict the risk for each person, so they can make lifestyle choices to help reduce the risks. This includes the changes that happen in the genome when a cancer develops. By ananlysing the genomes of cancer cells, scientists and doctors hope to become even better at choosing the best treatment for each individual.

Question 48

🟢 How does Understanding the Human Genome help with understanding Human Evolution and History

Answer 48

Understanding the human genome helps us understand human evolution and history. People all over the world can be linked by patterns in their DNA, allowing sciemtists to trace human migration patterns from our ancient history. We can also be linked to early members of the human family tree. For example, most people have a small number of Neanderthal genes in their DNA, even though that branch of human family died out around 40,000 years ago.

Question 49

🟢 How many bases on DNA code for one amino acid?

Answer 49

Three bases on DNA code for one amino acid. Amino acids are joined together to make a protein. It is the particular sequence of amino acids that gives each protein a specific shape and function.

Question 50

🟢 What 4 bases pair up

What bases pair with GATTACA

Answer 50

A - T
C - G

CTAATGT

Question 51

🟢 What are Long Strands of DNA made up of

Answer 51

The long strands of your DNA are made up of alternating sugar and phosphate sections. These make up the backbone of the molecule. Attached to each sugar is one of four different compounds called bases.

Question 52

🟢 What letters are the bases represented by

Answer 52

The bases are respresented by the letters A, C, G, and T.

Question 53

🟢 What is a Nucleotide

Answer 53

The combination of a sugar, a phosphate, and a base is called a nucleotide. The DNA polymer is made up of repeating nucleotide units

Question 54

🟢 How are the Nucleotide Units grouped

Answer 54

The nucleotide units are grouped into threes, and each group of three bases codes for a particular amino acid. Each gene is made up of hundreds of thousands of these bases. The order of the bases controls the order in which the amino acids are assembled to produce a particular protein for use in your body cells. Each gene codes for a particular combination of amino acids, which make a specific protein. A change or mutation in a single group of bases can be enough to change pr disrupt the whole protein structure and the way it works.

Question 55

🟢 What holds the Double Helix Structure together in DNA and Why

Answer 55

The key to the strcuture and functioning of the DNA molecule is the way the bases join up. In the complemntary strands of the DNA molecule, a C is always linked to a G on the opposite strand. Similarly, T is always linked to A. This holds the structure of the DNA double helix together. It is also key in the way information from the genes on the DNA is translated into proteins of the cell.

Question 56

🟢 How Does Protein Synthesis Occur

Answer 56

Protein syntehsis in the cell is controlled by the DNA in the nucleus in a sophisticated series of steps.

Genes in the DNA produce a template for the proetin. The template reflects the sequence if bases in the DNA, but is small enough to leave the nucleus through the pores in the nuclear membrane.

• The template leaves the nucleus and binds to the surface of a ribosome
• The cytoplasm contains carrier molecules, each attached to a specific amino acid. The carrier molecules attach themselves to the template in the order given by the DNA.
• The amino acids are joined together to form a specific protein
• Carrier molecules keep bringing specific amino acids to add to the growing protein chain in the correct order until the tenplate is completed.
• The protein detaches from the carrier molecules and the carrier molecules detach from the template and return to the cytoplasm to pick up more amino acids.

Question 57

🟢 What happens once the Protein Chain is Complete in Protein Synthesis

Answer 57

Once the protein chain is complete, the molecule folds up to form a unique shape that will enable it to carry out its functions in the cell. For example, if the protein is going to act as an enzyme, it will fold to produce an active site. If it is going to act as a hormone, or a clotting factor in blood, or a muscle, or part of the structure of the cell membrane, the proetin will fold so it can carry out its specific job in the cell. This is how DNA controls protein synthesis.

Question 58

🟢 What Happens if there is any change in the order in the Bases

Answer 58

Any change in the order of the bases in the DNA structure of a gene will alter the template that is made. A different template may result in a different sequence of amino acids joining together and so result in a change in the protein synthesised by a gene.

Question 59

🟢 What are Chromosomes? (+What is the name of the regions they are divided up into)

Answer 59

Chromosomes are long, coiled molecules of DNA that are divided up into regions called genes.

Most body cells contain chromosomes in matched pairs. The number of pairs of chromosomes varies between species. Human body cells have 23 pairs of chromosomes in the nucleus.

Question 60

🟢 What are Genes and their Function

Answer 60

• Along the length of each chromosome are shorter sections of DNA called Genes.
• Each gene has coded genetic information, in the form of base pairs.
• Each gene contains a different code that makes a specific protein.
• Proteins are needed for growth and repair of cells.

Question 61

🟢 What is Genetic Code and how does it work

Answer 61

• The genetic code is formed by the pairing up of base pairs.
• There are 4 base pairs A, T, G and C.
• Each gene contains a different sequence of base pairs.
• A gene codes for a specific amino acid which in turn makes a specific protein.

Question 62

🟢 What is DNA made up of and how is it structured?

Answer 62

DNA is a polymer made from four different nucleotides.

Each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to the sugar

DNA contains four bases A, C, G, and T. A sequence of 3 bases is the code for a particular amino acid

The order of bases controls the order in which amino acids are assembled to produce a particular protein

The long strands of DNA consist of alternating sugar and phosphate sections. Attatched to each sugar is one of the four bases.

Question 63

🟢 What is a gene that is said to be Expressed, and what does the Non-Coding part of DNA do?

Answer 63

When a gene codes for a protein that is syntehsised in the cell, the gene is said to be expressed. Most of the DNA does not actually code for proteins. Scientists are still discovering what the non-coding part of the DNA does. One thing they have discovered is that the non-coding parts of the DNA are involved in switching genes, or parts of genes, on and off. The non-coding DNA is part of the answer to the question of how we can synthesise so many different chemicals with so few genes.

Each gene can control synthesis of lots of different proteins. This may depend on how much if a gene is switched in or off, or which other genes are switched on or off at the same time. Scientists think that variations in the non-coding areas of our DNA may affect how are genes are expressed. This then affects the phenotype - this physical appearance or biochemistry of an organism.

Question 64

🟢 What are Mutations and why do they happen

Answer 64

New forms of genes result from changes in existing tenes and these changes are what we call mutations. They are often tiny changes in the sequence of bases in a strand of DNA. Mutations occur all the time, often as a result of mistakes made in copying the DNA for new cells as they reproduce. Most do not alter the protein, or only alter it slightly so that its appearance or function is not changed.

Question 65

🟢 What thing happens as a result of Mutations in the Coding DNA

Answer 65

When mutations take place in the coding DNA, most do not alter the protein formed, or alter it so slightly that its appearance and function is not changed.

Question 66

🟢 What thing happens as a result of Mutations coding for a change in the Amnio Acids

Answer 66

A few mutations code for a change in the amino acids that results in an altered protein that folds to give a different shape. As a result, the active site of an enzyme may no longer fit the substrate, or structural protein may lose its strength.

On the other hand, the changes caused by a mutation may give an advantage, e.g producing a more efficient enzyme or a stronger structural protein.

Question 67

🟢 What happens when Mutations occur in the Non-Coding DNA

Answer 67

When mutations take place in the non-coding DNA, it does not directly affect the phenotype. However, variants in the non-coding DNA can affect which genes are switched on or switched off. By changing the genes that are expressed, changes in the non-coding DNA can have a big effect on the phenotype of the organism. So variations in these areas of DNA may affect how genes are expressed.

Question 68

🟢 How Does Inheritance Work

Answer 68

The chromosomes you inherit carry your genetic information in the form of genes. Many of these genes have different forms, or alleles (sometimes called varients). Each allele codes for a different protein. The combination if alleles you inherit will determine your characteristics. We can make biological models that help us with predicting the outcome of any genetic cross

Question 69

🟢 Homozygote Definition

Answer 69

An individual with two identical alleles for a characteritsic, for example, BB or bb

Question 70

🟢 Hetrozygote Definition

Answer 70

An individual with different allels for a characteristic, for example, Bb

Question 71

🟢 Genotype Definition

Answer 71

The genetic makeup of an individual regarding a particular characteristic

Question 72

🟢 Phenotype Definition

Answer 72

The physical appearance of an individual regarding a particular characteristic

Question 73

🟢 Dominant (Allele) Definition

Answer 73

Alleles which will always be expressed in the phenotype when it is present. It is shown as a capital letter, for example, B

Question 74

🟢 Recessive (Allele) Definition

Answer 74

Alleles that can be masked by a dominant one, so they will only be expressed in the phenotype in the absence of a dominant allele. It is shown as a lower case letter, for example, b

Question 75

🟢 Allele Definition

Answer 75

Alternative forms of a gene

Question 76

🟢 Gametes Definition

Answer 76

The sex cells (ova and sperm in animals, ovules and pollen in plants). They only contain one set of chromosomes so can only carry one of the two alleles that the parents have in their cells

Question 77

🟢 Offspring Definition

Answer 77

The generation resulting from reproduction

Question 78

🟢 What Characteristics are controlled by single Genes (+ How many Genes are most characteristics controlled by)

Answer 78

Some characteristics are controlled by a single gene, such as: fur colour in mice; and red-green colour blindness in humans. Each gene may have different forms called alleles.

Most characteristics are a result of multiple genes interacting, rather than a single gene.

Question 79

🟢 What are Alleles and how do they Work

Answer 79

An allele is the particular form of information in that position on an individual chromosome. The alleles present in an individual, known as the genotype, work at the level of the DNA molecules to control proteins made.

The alleles present, or genotype, operate at a molecular level to develop characteristics that can be expressed as a phenotype.

Question 80

🟢 What are Dominant Alleles and How are they Shown

Answer 80

A dominant allele is always expressed, even if only one copy is present.

Dominant alleles are always expressed with a captial letter, so for brown eyes, the dominant allele would be the letter B.

Question 81

🟢 What are Recessive Alleles and How are they Shown

Answer 81

A recessive allele is only expressed if two copies are present (therefore no dominant allele present).

Recessive alleles are always expressed with a lower case letter, so for blue eyes, the recessive allele would be the letter b.

Question 82

🟢 What are Genetic Crosses

Answer 82

A genetic cross is when you consider the potential offspring that might result from two known parents. Remeber that you need to look at bogh the possible genotypes and possible phenotypes of the offspring.

Question 83

🟢 What are Punnet Squares, What do they Do, and What do they Show

Answer 83

You can model genetic crosses using a genetic diagram such as a Punnet Square to predict the outcome of different genetic crosses. A genetic diagram gives us:

• The alleles for a characteristic carried by the parents (the genotype of the parents)
• The possible gametes that can be formed from these
• How these may combine to form the characteristic in their offspring. The possible genotypes of the offspring allow you woek out the possible phenotypes too.

Question 84

🟢 Example Question:

A black haired heterozygous man and a blonde haired female are having a child. What is the % probability of the child having black hair?

Use a Genetic Cross and a Punnet Square to show why.

Answer 84

Key:
B = Black hair b = blonde hair

Parent Phenotype: Black hair x Blonde hair

Parents genotype: Bb x bb

Sex Cells: (gametes) B, b (sperm) x b, b (egg)

Genetic Cross:

———|———–|——–
| b | b
———|———–|——–
B | Bb | Bb
———|———–|——–
b | bb | bb
———|———–|——–

Offspring Phenotype: Black hair, Black hair, blonde hair, blonde hair

Offspring genotype: Bb, Bb, bb, bb

Probability (%): 50% chance of black hair, 50% chance of blonde hair

Question 85

🟢 What are 2 examples of inherited disorders and are they dominant or recessive

Answer 85

Some disorders are inherited. These disorders are caused by the inheritance of certain alleles.

• Polydactyly (having extra fingers or toes) is caused by a dominant allele.
• Cystic fibrosis (a disorder of cell membranes) is caused by a recessive allele.

Question 86

🟢 Find out the probability if someone will be a carrier and a sufferer of cystic fibrosis if both parents are carriers.

Answer 86

Key:
C - dominant allele, c - recessive allele

CC - ‘normal’
Cc - carrier
cc - sufferer (has Cystic Fibrosis)

Parent Phenotype: Carrier x Carrier

Genotype: Cc x Cc

Gametes:
C,c
C,c

Punnet Square:

———|———–|——–
| C | c
———|———–|——–
C | CC | Cc
———|———–|——–
c | Cc | cc
———|———–|——–

Ratio for a Sufferer: 3:1 (25% affected by Cystic Fibrosis)

Ratio for a Carrier: 1:1 (50% chance of carrying the faulty allele)

Ratio for being ‘normal’: 1:3 (25% totally unaffected)

Question 87

🟢 Find out the probability if someone will suffer from Polydactyly if one parent has it, and one doesn’t.

Answer 87

Key:
P - dominant allele, p = reccesive allele

PP - Has Polydactyly
Pp - Has Polydactyly
pp - ‘normal’

Parent Phenotype: Has Polydactyly x Doesn’t have Polydactyly

Genotype: Pp x pp

Gametes:
P,p
p,p

Punnet Square:

———|———–|——–
| P | p
———|———–|——–
p | Pp | pp
———|———–|——–
p | Pp | pp
———|———–|——–

Ratio: 1:1 for Suffering from Polydactyly

Probability: 50% Suffer From Polydactyly, 50% are unaffected

Question 88

🟢 What Is Polydactyly, is it Dominant or Recessive

Answer 88

When babies are born with extra finger or toes, they have polydactyly. The most common form of polydactyly is caused by a dominant allele. It can be inherited from one parent who has the condition. People often have their extra digit removed, but some people live quite happily with them.

Question 89

🟢 What are the chances of passing Polydactyly on

Answer 89

If you have polydactyly and are hetrozygous, you have a 50% chance of passing on the disorder to any child you have. That’s because half of your gametes will contain the faulty dominant allele. If you are homozygous, your children will definitely have the condition.

Question 90

🟢 What Other Dominant Genetic Diseases Have More Widespread Effects Than Polydactyly

Answer 90

Some dominant genetic disorderd have a much more widespread effect on the way the body works than polydactyly. For example, Huntington’s disease is a dominant genetic disorder, in which symptoms develop in middle age. It affects the nervous system and eventually leads to death.

Question 91

🟢 What is Cystic Fibrosis and what does it do/affect?

Answer 91

Cystic fibrosis is a genetic disorder that affects many organs of the body, especially the lungs, the digestive system, and the reproductive system. Over 8500 people in tne UK have cystic fibrosis.

Cystic fibrosis is a disorder of the cell membranes that prevente the movement of certain substances from one side to the other. As a result, the mucus made by cells in many areas of the body becomes very thick and sticky. Organs, especially the lungs, can become clogged up by the thick, sticky mucus, which stops them from working properly. The pancreas cannot make and secrete enzymes properly because the tubes through which the enzymes are released into the small intestine are blocked with mucus. The reproductive system is also affected, so many people with cystic fibrosis aee infertile.

Question 92

🟢 What Treatment is there for Cystic Fibrosis?

Answer 92

Treatment for cystic fibrosis includes physiotherapy and antibiotics to help keep the lungs clear of mucus and infections. Enzymes are used to replaced the ones the pancreas cannot produce and to thin the mucus.

However, although treatments are getting better and better over time, there is still no cure for this disorder.

Question 93

🟢 Is Cystic Fibrosis Dominant or Recessive, and what are the chances of passing it on and how

Answer 93

Cystic fibrosis is caused by a recessive allele so it must be inherited from both parents. Children affect by cystic fibrosis are usually born to parents who do not suffer from the disorder. The parents have a dominant, healthy allele, which means their bodies work normally. However, they also carry the recssive cystic fibrosis allele. Because it gives the m no symptoms, they have no idea it is there. They are known as carriers.

Question 94

🟢 How is Cystic Fibrosis Passed On and what are the chances of a child inheriting it?

Answer 94

The only situation when it may become obvious is if a carrier has children with another carrier of cystic fibrosis. When looking at the possibility of inheriting genetic disorders, it is important to remember that every time an egg and a sperm fuse it is down to chance which alleles combine. So if two parents who are hetrozygous for the cystic fibrosis allele have 4 children, there is a 25% chance that each child will have the disorder.

All 4 children could have cystic fibrosis, or none of them might be affected. They might all be carriers, or non of them might ingerit the faulty alleles at all. It’s down to chance.

Question 95

🟢 Can Genetic Disorders be cured right now, and what do doctors hope can cure it?

Answer 95

So far, scientists have no way of curing genetic disorders, even those that are very serious and can shortenlives. Scientists hope that genetic engineering will be the answer, allowing them to replaced faulty alleles with healthy ones. Currently, scientists are working on a gene replacement for cystic fibrosis and are beginning to make progress in halting the disease and improving lung fumction. Unfortunately, so far they have not managed to cure anyone with an inherited disorder, but remain hopeful of this possibility.

Question 96

🟢 *What are the 2 Ways An Embryo or Fetus is Screened

Answer 96

To screen an embryo or fetus, you need to harvest some cells from the developing individual. The two main methods that can be done during pregnancy includes:

Amniocentesis:
It’s carried out at around 15-16 weeks of pregnancy. It involves taking some of the fluid from around the developing fetus. This fluid contains fetal cells, which can then be used for genetic screening.

Chronic Villus Sampling:
Chronic villus sampling of embryonic cells is done at an earlier stage of pregnancy - between 10 and 12 weeks - by taking a small sample of tissue from ghe developing placenta. This again provides fetal cells to screen

Question 97

🟢 What are Some Downsides of Amniocentesis and Chronic Villus Sampling

Answer 97

Both tests have an associated risk causing a miscarriage, but are currently the main methods used to obtain fetal cells for screening. New methods that depend on analysing fetal cells found in the blood of the mother offer the promise of much less invasive testing the future.

Question 98

🟢 *What Is The Alternative to Amniocentesis and Chronic Villus Sampling

Answer 98

Another alternative taken by some couples with an inherited disorder in the family is for embryos produced by IVF to be tested before they are implanted in the mother, so only babies wothout that disorder are born.

Question 99

🟢 How Is Screening for Genetic Disorder Carried Out

Answer 99

Once cells have been collected from an embryo or fetus - either before implantation or by techniques such as aminocentesis and chorionic villus sampling - they need to be screened. Whatevee the potential genetic problem, the screening process is similar. DNA is isolated from the embryo cells and tested for specific disorders.

Question 100

🟢 What choices can Parents make if Genetic Disorder Screening shows the fetus is affected

Answer 100

If the screening shows that a fetus is affected, the parents have a choice. They maydecide to keep the baby, knowing that it will have a genetic disorder when it is born. On the other hand, they may decide to have an abortion or to not process with implantation. This prevents the birth of a child with serious problems. Then the parents can try again to have a healthy baby. They may choose to have pre-implantation embryo screening using IVF to avoid having another affected pregnancy.

Question 101

🟢 Advantages For Embryonic Screening

Answer 101

• It will help to stop people from suffering.
• Treating disorders costs the Government (and the taxpayers) a lot of money
• There are laws to stop it going too far. At the moment, parents cannot even select the sex of their baby (unless it’s for health reasons)

Question 102

🟢 Disadvantages Against Embryonic Screening

Answer 102

• It implies that people with genetic problems are ‘undesirable’ - this could increase prejudice
• There may become a point where everyone wants to screen their embryos so they can pick the most ‘desirable’ one, e.g they want a blue-eyed, blonde haired, intelligent boy
• Screening is expensive
• The screening (and knowing in advance) of any disorders allows families and parents to be as prepared as possible.
• Although screening is becoming more accurate and reliable, they can sometimes give false results. This can, ocasionally lead to the termination of a healthy baby or unexpected birth of a child with a genetic disorder
• Embryo screening also means people have to make decisions on whether or not to terminate a pregnancy. This is never an easy decision, and they end up making choices based of scientific understanding and their own emotions based on their ethics and beliefs