Topic 3- Genetics (2)

Question 1

What animals does asexual reproduction occur in?

Answer 1

It’s more common in (invertebrates) such as insects

Question 2

What is a zygote and what does it contain?

Answer 2

A fertilised egg. They carry instruction that control each individual cell and also shape, coordinate and control our bodies.

Question 3

What is the genome?

Answer 3

The DNA of an organism. Most cells contain a complete copy of an organisms genome

Question 4

Where is the genome found and what is a gene?

Answer 4

The human genome is found in 46 very long molecules of DNA and each molecule is inside a chromosome. Along the length of a DNA molecule are sections that each contain a code for making a protein. These DNA sections are called genes.

Question 5

What are polymers?

Answer 5

These are proteins made by linking different amino acids together in a chain. The order of the amino acids is controlled by a gene.

Question 6

What is meiosis?

Answer 6

Meiosis is used to produce gametes (haploid cells). Each chromosome replicates. The two copies remain attached making each chromosome look like an X. The two sets of chromosomes ‘pair up’ forming 23 pairs and then separate into 2 new cells. Meiosis produces four haploid daughter cells.

Question 7

Why are gametes different?

Answer 7

Each chromosome in a pair contains different versions of the same genes. They are genetically different. So gametes are all different because they contain genetically different chromosomes.

Question 8

What is the process of meiosis?

Answer 8

• the cell starts of with a pair of chromosomes. It is diploid.
• the chromosomes replicate (and the copies stay stuck to one another)
• the cells divide into 2 and then into 2 again. each of the final four daughter cells are has a copy of one chromosome from each pair. (The are haploid)

Question 9

What is the shorter version of writing haploid of diploid?

Answer 9

Diploid - 2n

Haploid - 1n

Question 10

What is DNA?

Answer 10

The nuclei of your cell contains very long molecules of DNA. Each molecule is tightly coiled and packaged up form chromosomes.

Question 11

What does a molecule of DNA contain?

Answer 11

A molecule of DNA contains two strands, each of which forms a shape called a helix. The two strands are joined together by pairs of substances bases, to form a double helix.

Question 12

What are the four bases?

Answer 12

A= adenine
T= Thymine 
C= cytosine
G= guanine 

Often refer it then by their first letters.

Their complementary base pairs are:
C-G
A-T

Question 13

What is a nucleotide and what is each base attached too?

Answer 13

Each base is attached to a sugar (deoxyribose) and each sugar is attached to a phosphate group. This grouping combine is called a nucleotide.

Question 14

What do the bases, deoxyribose and phosphate form in DNA?

Answer 14

The sugars and phosphate groups form the backbone of the DNA strands. DNA is therefore made of many similar sub units joined in a chain and so it’s a polymer.

Question 15

What is hydrogen bonding?

Answer 15

Parts of a DNA base have very slight electrical charge. A slightly negatively charged base attracts Tina slightly positively charged base. This from a a weak force of attraction called a hydrogen bond.

C-G form 3 hydrogen bonds between them and A-T only form two hydrogen bonds between them which helps to explains why C only pairs to G and A only pairs to T.

Question 16

What is the DNA code?

Answer 16

The order of bases in a gene contains the coded instructions for a protein. However, we all have slight differences in our genes caused by slightly different orders of bases in out DNA. Except identical twins.

Question 17

What did Me del do to prove that people to not have ‘blended’ characteristics from their parents?

Answer 17

Mendel observed many characteristics in pea plants that, like red hair, were either present or absent but not a ‘blend’ Mendel set about developing some rules fir how they where inherited.

Question 18

How did he prove that people did not have ‘blended’ characteristics?

Answer 18

He bred (cross bred) pea plants together by using a paintbrush to move pollen (containing male gametes) from one plant to another . A bag was then placed over the flower on the plant and sealed. He then planted the seeds formed and observed the characteristics of the offspring.

Question 19

What is Mendel conclude after the experiment?

Answer 19

He concluded that inherited ‘factors’ control the variations of characteristics. These factors exist in different versions (alleles) that do not change. A plant has two factors for each characteristic
, which are either the same version or two different versions.

Question 20

What were Mendel’s three laws of inheritance?

Answer 20

1- each gamete receives only one factor for a characteristic.

2- the version of a factor that a gamete receives is random and does not depend on the other factors in the gamete.

3- some versions of a factor are more powerful than others and always have an effect in the offspring.

Question 21

What is an allele?

Answer 21

Different forms of the same gene.

E.g genes for the same characteristic (eye colour) can contain slightly different instructions that create variations (e,g brown, blue)

Question 22

Why does our body contain two copies of every gene?

Answer 22

Because there are two copies of every chromosome in a body cell nucleus.
Each copy of a gene may be a different allele. There are many alleles for most of the genes in our body. The different combination of alleles in each person gives us slightly different characteristics (genetic variation)

Question 23

What is the difference between homozygous and heterozygous?

Answer 23

If both alleles for one gene are the same an organism is homozygous for that gene. If the alleles are different, an organism is heterozygous.

Question 24

What is a recessive characteristic and when is it seen?

Answer 24

A recessive characteristic is only seen if both alleles are recessive. This can be shown in a genetic diagram.

Question 25

How are dominant and recessive allele shown?

Answer 25

A dominant allele is shown by a capital letter (e.g R for purple) the recessive allele has the lower case version of the same letter(e.g r for not purple) the letter for the dominant allele is always written first.

Question 26

What is the genotype and phenotype of an organism?

Answer 26

The alleles in an organism is its genotype and what an organism looks like is its phenotype.

Question 27

What is a genetic diagram?

Answer 27

Shows the possible combinations of alleles when two organisms breed. We use diagrams like this to explain the inheritance of one gene (mono hybrid inheritance). We can also use these diagrams to predict the ratios of the phenotype.

Question 28

What are two sex chromosomes?

Answer 28

Two of your chromosomes are sex chromosome and determine what sex you are. The are two types X and Y. Females have two sets of X and makes have one X and one Y.

Question 29

What sex chromosomes do males and females contain?

Answer 29

A woman’s gamete (egg cell) always contains an X sex chromosome but male sperm contains either an X or a Y.

Question 30

What is a punnet square?

Answer 30

Punnet squares are used to work out the theoretical probability of offspring inheriting certain genotypes. They are also used to work out the probabilities of different probabilities caused by alleles.

Question 31

When giving a blood transfusion why does the blood have to be the same?

Answer 31

The blood they are given must be the same otherwise the red blood cells will climb together which can kill.

Question 32

What is the ABO blood groups?

Answer 32

One of the ways of classifying different types of blood groups. Everyone’s blood group is one of four groups?
A, B, AB or O. Which blood group your are determines weather you have certain marker molecules on the outside of your red blood cells. There are three types of marker A, B, O.

Question 33

How is the gene responsible for the markers of ABO written?

Answer 33

It has 3 alleles written as

IA, IB, IO (second letter is written as an indice at the top.

Question 34

What does codominant mean?

Answer 34

When both alleles for a gene affect the phenotype we say it is codominant.

Everyone has two copies of the gene so may be homozygous for a y three alleles or heterozygous for any two of the three alleles. IO is recessive to both IA and IB. However a person with a genotype IAIB shows the effect of both alleles and has the blood group AB.

Question 35

What is the variation in eye colour caused by?

Answer 35

Caused by the OCA2 gene which controls the amount of melanin produced. Melanin is a protein that makes hair, eye and skin darker in colour. The lighter the colour the less melanin. E.g a blue iris contains little melanin while a brown iris contains a lot of melanin.

Question 36

What is a mutation?

Answer 36

A change in a gene that creates a new allele is called a mutation. Mutations often occur in cell division.

Question 37

When do mutaions happen?

Answer 37

Mutations happen when there is a mistake in copying DNA during cell division. For example one base in a DNA sequence might be replaced with another. This can happen naturally but is more likely to happen if there is damage to the DNA caused by radiation of certain substances.

Question 38

What affect do mutations have?

Answer 38

Sometimes a mutations produces an allele that causes a bug change in protein that is produced. This will affect how the body works. However, mutations can occur in different parts of a gene and so may only have a small effect on the protein produced. Some mutations may not change the protein so will not affect the phenotype.

Question 39

What is the Human Genome project?

Answer 39

It involves scientists in many different countries. The project produced a map of 3.3 billion complementary base pairs in in one set if 46 human chromosomes.

Question 40

What causes genetic variation?

Answer 40

Caused by different alleles inherit during sexual reproduction.

Question 41

What is environmental variation?

Answer 41

When an organisms characteristic is affected by its surroundings.

Question 42

What does acquired characteristics mean?

Answer 42

Characteristics that are changed by the environment during the life of the individual. E.g loss of a limb in an accident.

Question 43

What are two types of variations and how are they different?

Answer 43

Discontinuous variation: where data can only take a limited set of values.
Continuous variation: where the data can be any value in a range.

Question 44

Compare and mitosis and meiosis?

Answer 44

Mitosis is cell division that produces two diploid daughter cells from one parent cell. During mitosis each daughter cell receives a copy of every chromosome in the parent cell. Which means that they are genetically identical. Mitosis is used in asexual reproduction and produces offspring that are genetically identical to one parent.

In meiosis four daughter cells are produced from one parent cell. Each daughter cell haploid and has copies of only half the chromosomes of the diploid parent cell. This produces gametes that are genetically different to each other. Meiosis occurs before sexual reproduction and produces in which two gametes fuse to form a fertilised egg cell that is diploid. The variation in the gametes mean the offspring differ genetically from each other and from the two parents.

Question 45

What is the genetic code?

Answer 45

Matches codons to specific amino acids.

Question 46

What causes a mutation or a genetic variation?

Answer 46

A change in bases of a gene. It can be caused when DNA is not copies properly or when a base is deleted causing a big change in all bases. Environmental conditional can also cause mutations such as exposure to radiation. This can be seen in the phenotype.

Question 47

Wha affect do alleles have and what are their affect?

Answer 47

They exist because of mutations. one gene can have many alleles caused by mutations. Your characteristics are shaped by the alleles you inherit.

Question 48

What does the haemoglobin contain?

Answer 48

It contains 4 polypeptides of two kinds. a and ß.

Question 49

What do the polypeptides in the haemoglobin do?

Answer 49

The polypeptides fold and join up to form a globular protein, which carry’s oxygen.

Question 50

What does sickle cell disease do to you blood cells and how is it caused?

Answer 50

If a polypeptide folds incorrectly it can cause this. Red blood cells become sickle shaped and join together resulting in an episode of extreme pain lack of oxygen.

Question 51

What causes genetic disorders?

Answer 51

Mutations.

Question 52

How might a mutation result in RNA polymerase not binding well and what is the effect?

Answer 52

RNA polymerase attaches to the DNA bases in front of the gene. A mutation in this non coding reason may result in the RNA polymerase not binging well, which reduces transcription.

Question 53

Why are the symptoms of ß thalassaemia?

Answer 53

Tiredness
Weakness
Shortness of breath

Question 54

Do non coding mutations always cause harm?

Answer 54

No other non coding mutations can mutations can result in RNA binding better and producing more mRNA.