Reprpduction And Inheritance

Question 1

Explain the process of translation

Answer 1

1)the mrna strand travels through the cytoplasm and attaches to the ribosome
2)tRNA molecules, which have a specific anticodon on them, pair with the complementary triplet (codon) on the mrna
3)tRNA molecules also have a site in them where amino acids can attach to, so the tRNA molecules bring with it it’s specific amino acid
4)the ribosome moves across the mrna strand, and another tRNA molecule moves in, brining with it it’s specific amino acid
5)used tRNA molecules leave the ribosome to collect another amino acid
6) the process continues until a stop codon is reached on the man’s strand
7) and so a polypeptide chain, which consists of a chain of many amino acids bonded by peptide bonds is formed. This then folds into shape to produce a specific protein.

Question 2

What is a gene

Answer 2

A section of dna that codes for a particular protein

Question 3

Describe the structure of dna

Answer 3

A nucleic acid, a chemical.
Which is a polymer, made up of small units called nucleotides
Each nucleotide is made up of a sugar, phosphate and a base,
And many nucleotides join together to form 2 strands cooled together, which is called a double helix structure

Question 4

What is a karyotype

Answer 4

A diagram, which shows a full set of human chromosomes

Question 5

Every nucleotide has the same… and…. But different……

Answer 5

Sugar, and phosphate group,
bases

Question 6

Stats the exact names of the parts of a dna nucleotide

Answer 6

(Pentose) Sugar deoxyribose
Phosphate
Basée (ATGC)

Question 7

Give three examples of proteins

Answer 7

-structural proteins like keratin,
-enzymes
-hormones

Question 8

State three differences between DNA and RNA

Answer 8

Dna consists of two strands whereas rna consist of 1 strand
Dna contains the sugar deoxyribose, but rna consists of the sugar ribose
Dna contains the bases guanine, cytosine, adenine, thymine, BUT RNA consists of the bases guanine, cytosine, adenine, uracil

Question 9

What is a genome

Answer 9

The entire dna that makes up an organism

Question 10

Explain the process of mitosis

Answer 10

Interphase: -Before mitosis, chromosomes are replicated to form exact copies of themselves, called sister chromatids, forming the x shape chromosome
Prophase: -the chromatids condense and become more visible
-and each cheomome is joined by a centromere.
-the nuclear membrane also breaks down
Metaphase:-the chromosomes line up on top of each other at the equator, and spindle fibers attach at the centromere
Anaphase: the spindle fibers shorten and pull apart the sister chromatids to opposite poles of the cell
-the chromomes have separated now to form a full set of homologous chromosomes for 2 daughter cells
Téléphase: nucleus forms at the poles of the cell as the cytoplasm divides,
- with a full set of 46 chromosomes, and so two daughter nuclei have been formed
-which are identical to the parent

Question 11

Explain the process of meiosis

Answer 11

1)chromosomes replicate themselves and line up at the equator in random order
2)during the first division, chromosomes are pulled apart by spindle fibers, where one chromosome from each homologous park will go into a different daughter cell.
-two diploid daughter cells will be formed, each having 46 chromosomes
3)-in the second division, the chromosomes line up again at the equator and are pulled apart by spindle fibres
-the cells are divided again into four daughter cells, where now each cell is haploid and so contains only 23 chromosomes
4)all the gametes will be genetically different to each other, due to the random shuffling of maternal and paternal chromosomes in each cell, so they have different combinations of alleles

Question 12

How does….. being about genetic variation

Answer 12

Meosis
Because there is a random shuffling of maternal and paternal chromomes in each gamete
Therefore the offspring will have a different combination of alleles

Question 13

Give three uses of mitosis

Answer 13

-produces all cells of the body apart from gametes
-repairs and replaces damaged tissues
-important for asexual reproduction because it produces offspring which are genetically identical to the parent

Question 14

Give two uses of meosis

Answer 14

-produces gametes
-important for bringing about genetic variation among offspring

Question 15

Give four differences between mitosis and meiosis

Answer 15

Mitosis results in produces diploid daughter cells, but meosis haploid daughter cells
Mitosis produces body cells, meosis produces gametes
Mitosis produces 1 daughter cells, so 2 divisions, meosis produces 4 daughter cells so 2 division
Mitosis does not result in genetic variation, meosis does result in genetic variation

Question 16

Explain the process of transcription

Answer 16

1)dna is too large to leave the nucleus, therefore help case enzyme “unzips” and “unwinds” the two strands of dna , as the hydrogen bonds between the complimentary base pairs break
2)the template strand of dna is exposed, which will form the framework for mrna to form
3)rna polymerase attaches to the dna strand and moves across it
4) free rna nucleotides base pair with the complimentary dna bases, to form a strand of mrna
5)mrna is now an exact copy of dna, (except that thymine is replaced with uracil) and so leaves the nucleus through the cytoplasm and attaches to a ribosome

Question 17

During transcription, how is helicase enzyme able to unzip and unwind the two strands of dna

Answer 17

Because it breaks the hydrogen bonds between the complimentary base pairs

Question 18

In rna, uracil replaces….

Answer 18

Thymine

Question 20

Phenotype meaning

Answer 20

Observable characteristics of an organism

Question 21

Give the six stages needed to be included inside a monohybrid cross

Answer 21

1)parents phenotype
parents genotype
Parents gametes
Punnet square
Offspring genotype
Offspring phenotype

Question 22

Explain the difference between monohybrid inheritance and polygenic inheritance

Answer 22

Monohybrid is inheritance of characteristics, controlled only by a single gene
Polygenic inheritance is inheritance of characteristics, controlled by more than one gene, therefore it can result in many different phenotypes

Question 23

Inheritance of sex depends upon….

Answer 23

The sperm cell from the male has , because only he Carrie’s the xy chromosome

Question 24

Every time offspring is produced, there is a …. Chance of it being girl and… chance of it being boy

Answer 24

50%

Question 25

Give an example of codominance, and state which alleles are dominant over which

Answer 25

Blood group
I^A and I^B are dominant over I^O
Whereas I^A and I^B are codominant

Question 26

What is codominace

Answer 26

When neither allele is dominant over the other, so both alleles within the genotype are expressed

Question 27

What is a genotype

Answer 27

The combination of alleles that control a characteristic

Question 28

Explain how there is genetic variation in human offspring

Answer 28

Because firstly, each gamete has a different variation of maternal and paternal chromosomes due to meosis, therefore they each have a different combination of alleles
And because the fusion of the sperm and egg cell are random (any one sperm can fuse with any one egg)

Question 29

State the three types of ways genetic variation can occur and give examples

Answer 29

Genetic- eye colour
Environmental -mass because of diet
Both - height

Question 30

What is a mutation

Answer 30

A change in the dna base sequence,
Which is a rare and random change and can be inherited

Question 31

Describe two ways in which the risk of mutations can increase

Answer 31

Being exposed to gamme or x rays, because these are ionizing radiation, which can damage base sequences
Carcinogens

Question 32

Explain how a mutation can change a phenotype

Answer 32

1)mutation occurs and so the order of bases in a gene is changed
2)because each triplet codes for a specific amino acid, the sequence of amino acids changes
3)and because a particular amino acid codes for a particular protein, the shape will change and so it will code for an the entire different protein

Question 33

Express two ways in which mutations can occur which is normal

Answer 33

Alleles are the result of a mutation, because they are different forms of the same gene
Happens spontaneously in cells when dna is duplicated during mitosis

Question 34

Explain why most mutations have no effect on a phenotype

Answer 34

Because most dna is non coding, so doesn’t even code for a specific protein

Question 35

What is non coding dna

Answer 35

One that doesn’t code for any particular protein
And can control whether a gene is expressed or not express

Question 36

Give examples of two ways that mutations can be harmful

Answer 36

They can damage the shape of the active site of an enzyme, so that it can no longer form enzyme substrate complexes

In the disease called sickle cell anemia, where the shape of haemoglobin is altered, so red blood cells become stiff and sticky, so it can block narrow blood vessels and so prevent the flow of blood

Question 37

Explain Darwin’s theory of evolution

Answer 37

That within a species there is variation
This variation means that there is competition between offspring, so those most suited for the environment will have a higher chance of surivival,
Therefore those most well adapted with the most advantageous phenotypes will survive and reproduce, passing on their alleles to their offspring, whilst the others will die out
This process continues over generations until the frequency of those with the advantageous phenotype increases and so is more common

Question 38

Evolution defintion

Answer 38

The gradual change in a populations inherited characteristics over time due to natural selection

Question 39

Natural selection defintion

Answer 39

The process where by individuals who are better adapted to the environment survive and reproduce

Question 40

What is speciation and how does it happen

Answer 40

Process where by a population becomes so different from each other that they can no longer interbreed
Happens When a species has been divided by a physical barrier such as a river, and so there are different environments
So these different selection pressures cause the species on each side to adapt accordingly by natural selection, and so overtime the species will evolve and these most advantageous phenotypes will be most frequent

Question 41

Give three ways in which antibiotic resistance can be controlled

Answer 41

Should not be prescribed for viral infections
Shouldn’t be prescribed for minor infections that the immune system is capable of handling
Patients should ensure that the course is finished, so that there are no bacteria left to mutate

Question 42

Explain how antibiotic resistance occurs

Answer 42

Within bacteria, there is variation, because random mutations occur all the time
One of these mutations however may be a mutation that is antibiotic resistant
When exposed to an antibiotic, those without this phenotype will die out, whereas the antibiotic resistant ones will not
Therefore there is less completion for survival for the resistant strains
So they pass on their alleles to their offspring and begin to reproduce rapidly
Overtime, the entire population becomes antibiotic because the frequency of this phenotype has increased and so it is hard to control

Question 43

Give two advantages of sexual reproduction and one disadvantage

Answer 43

There is variation within offspring, which is advantageous because species can better adapt to environmental changes and survive
Less genetic variation means more susceptible to disease

Disadvantage:
Difficult for isolated members to mate

Question 44

Give two advantages and two disadvantges of asexual reproduction

Answer 44

Advantages:
-only one parent required
-population can be increased rapidly

Disadvantages:
-offspring genetically identical so can less likely adapt to changes and so survive
-less genetic variation means entire population more susceptible to disease

Question 45

Give an example of the only time where a dominant gene may not be passed on

Answer 45

If the is spring has two heterozygous parents
(Because do a punnet square, and you get BB Bb Bb bb
So two recessive alleles will also be present)

Question 46

By looking at a family pedigree chart, how would you be able to tell if a disease was carried on by a recessive allele

Answer 46

Is recessive, than allele will be present by skipping generations
And there will always be a carrier present

Question 47

Describe three differences between natural selection and selective breeding

Answer 47

Natural selection is much slower process
In selective breeding the parents are chosen
There is no completion and survival of the fittest in selective breeding

Question 48

What does it mean if an organism is pure breeding

Answer 48

It means that it is homozygous for that particular characteristic

Question 49

Who is sex inheritance determined on and why

Answer 49

The male
Because his sperm can have either the x or the Y chromosome

Question 50

Explain how the number of chromosomes in the offspring are maintained, although the gametes only contain half the number

Answer 50

This is because gametes are made by meosis, so contain 23 chromosomes each, haploid number
But at fertilisation, the egg and speed cell fuse together,
So diploid cells are formed which contain a full set of chromosomes

Question 51

Dominant allele meaning

Answer 51

Type of allele always present in the phenotype
Even if only one copy is present in the genotype

Question 52

Even if a genetic disease is dominant, explain why the number of people who have the disease are still few

Answer 52

Because they are unlikely to reproduce,
Therefore the allele is rare

Question 53

Give three functions of testosterone

Answer 53

Develops male secondary characteristics eg oubic hair
Creates a sex drive
Produces sperm