Section 7 - Reproduction and Inheritance P2

Question 1

Where is FSH produced and what’s its function?

Answer 1

• produced in the pituitary gland
• causes ova to mature in one of the ovaries in a follicle
• stimulates the ovaries to produce oestrogen
• oestrogen then inhibits the release of FSH

Question 2

Where is LH produced and what’s its function?

Answer 2

• produced by the pituitary gland

- stimulate the release of an egg on day 14

Question 3

What is the shape of a DNA molecule?

Answer 3

• has two strands

- a double helix

Question 4

What are the four bases in DNA?

Answer 4

adenine
cytosine
guanine
thymine

Question 5

What are the two pairs of bases?

Answer 5

adenine - thymine

cytosine - guanine

Question 6

What is the pair of bases of DNA called?

Answer 6

complementary-base pairing

Question 7

What does DNA control?

Answer 7

the production of proteins in a cell (protein synthesis)

Question 8

What makes up proteins?

Answer 8

chains of amino acids

Question 9

What makes proteins unique?

Answer 9

each protein have its own number and order of amino acids

-amino acid chains fold up to give each protein a different specific shape

Question 10

What is required for the coding of one amino acid?

Answer 10

a sequence of three bases in a gene (a codon)

Question 11

How many possible codons are there?

Answer 11

since there are four bases:

there are 4 x 4 x 4 = 64 possible codons

Question 12

How many amino acids are there?

Answer 12

20

Question 13

What are non-coding regions of DNA?

Answer 13

• areas of DNA which don’t code for amino acids

- but they are still involved in protein synthesis

Question 14

What are the two stages by which proteins are made?

Answer 14

Transcription

Translation

Question 15

Where are proteins made and what by?

Answer 15

Proteins are made in the cell cytoplasm

They are made by Ribosomes

Question 16

Why is the process of transcription needed?

Answer 16

DNA is found in the cell nucleus and can’t move out because it is really big
-but the cell needs information from the DNA to get to the ribosomes in the cytoplasm so this is why transcription is needed

Question 17

What molecule does transcription use?

Answer 17

messenger RNA (mRNA)

• it is shorter and is only a single strand
• uses uracil (U) instead of thymine (T)

Question 18

Describe the process of transcription:

Answer 18

• RNA polymerase binds to a region of non-coding DNA in front of a gene
• two DNA strands unzip and the RNA polymerase moves along one strand of DNA
• it uses the coding DNA in the gene as a template to make mRNA, base pairing between the DNA and RNA ensures that mRNA is complementary to that gene
• once made, the mRNA molecule moves out of the nucleus and joins with a ribosome

Question 19

What is RNA polymerase?

Answer 19

the enzyme involved in joining together the base sequence to make mRNA

Question 20

Describe the process of translation:

Answer 20

• amino acids are brought to the ribosome by transfer RNA (tRNA)
• the order which the amino acids are brought matches the order of the codons in mRNA
• part of tRNA’s structure is called an anticodon (complementary to the codon), the codon and anticodon are paired
• amino acids are joined together by the ribosome (this makes a protein)

Question 21

What are codominant alleles?

Answer 21

Some characteristics are caused by codominant alleles

-when neither allele is recessive, so you show characteristics from both alleles

Question 22

How do you draw genetic diagrams for codominant inheritance?

Answer 22

draw a punnet square
draw a grid (3 x 3)
-put the possible gametes from one parent down one side and the other across the top
-in each of the middle squares fill in the pairs of letters (one from the column and one from the row), this shows all the possible combinations of the gametes

Question 23

What is an example of a codominant allele which determines a characteristic?

Answer 23

Blood type is determined by two codominant alleles (A and B) and one recessive one (O)

Question 24

What do mutations do to DNA?

Answer 24

Mutations change the sequence of the DNA bases in a gene, producing a genetic variant
-the sequence of DNA bases codes for an amino acid to make a protein, mutations sometimes lead to a change in the protein it codes for

Question 25

What is a genetic variant?

Answer 25

A different form of a gene

Question 26

What are enzymes?

Answer 26

Enzymes are proteins which need an active site with a very specific shape to be able to work properly

Question 27

What affect can genetic mutations have on enzymes?

Answer 27

A mutation could lead to a change in the shape of an enzyme’s active site, altering its function
A mutation could also stop the production of an enzyme all together

Question 28

How can mutations increase variation?

Answer 28

By leading to a different phenotype

Question 29

What do most mutations cause?

Answer 29

most have no affect on the phenotype, they are neutral
(if a mutation occurs in an unimportant region of DNA or a mutated codon still codes for the same amino acid or if the mutation occurs in the recessive allele)

Question 30

What do some mutations cause?

Answer 30

Some mutations have a small affect on the phenotype

if a change in an amino acid only has a slight effect on a protein’s structure

Question 31

What do very few mutations cause?

Answer 31

Very rarely, a mutation will have a significant effect on a phenotype
(can result in a very different protein that can no longer carry out its function (can be harmful and lead to cancer, or beneficial like getting a survival advantage))

Question 32

What can increase the chance of a mutation?

Answer 32

• exposure to ionising radiation

- chemicals called mutagens (e.g. chemicals in tobacco)