!!!⭐️Genetic Info, Variations And Relationships: Genetic Diversity And Adaptation

Question 1

What is a gene mutation?

Answer 1

Any change to the quantity of bases or base sequence in the DNA

Question 2

What does the fact the genetic code is degenerate mean for mutations?

Answer 2

That mutations don’t always result in a change in the amino acid sequence of the polypeptide.

Question 3

What are the 2 types of mutations?

Answer 3

Base substitution and base deletion or insertion

Question 4

What is base substitution?

Answer 4

Where a base is substituted for another and may result in a change of 1 amino acid because the base sequence is changed

Question 5

What is base deletion or insertion?

Answer 5

Where a base is deleted or inserted causing the number of bases to change

Question 6

Which type of mutation is more likely to produce a dysfunctional protein?

Answer 6

Base deletion or insertion is more likely to produce a dysfunctional protein than base substitution because it will affect multiple amino acids from the point of mutation causing the amino acid sequence of the polypeptide to be entirely different hence the polypeptide is unlikely to function correct because the sequence of bases in dna is read in triplets

Question 7

What are mutagenic agents? Name four of them.

Answer 7

• UV
• X rays
• Cigarette smoke from carcinogens
• HPV

Question 8

How do mutagenic agents increase the rate of spontaneous mutations?

Answer 8

By interfering with the DNA’s copying and repairing mechanisms

Question 9

What are the two forms of chromosome mutations?

Answer 9

• changes in whole sets of chromosomes

- changes in the number of individual chromosomes

Question 10

What are chromosome mutations?

Answer 10

Changes in the structure or number of whole chromosome

Question 11

What does polyploid mean?

Answer 11

When organisms have three of more sets of chromosomes rather than the usual two causing a condition polyploidy mostly found in plants

Question 12

When do mutations in the number of individual chromosomes occur and what does this result in?

Answer 12

In chromosome non disjunction because it results in a gamete having either one more or one fewer chromosomes and if fertilised with a gamete that has the normal complement of chromosomes the resultant offspring have more or fewer chromosomes than normal.

Question 13

What is chromosome non-disjunction?

Answer 13

When individual nom homologous pairs of chromosomes fail to separate during meiosis

Question 14

What does meiosis produce?

Answer 14

Four daughter cells which are haploid hence are gametes and have genetic variation

Question 15

What are the stages of meosis?

Answer 15

Interphase- homologous pair of chromosomes are replicated

Meiosis I - homologous pair of replicated chromosomes separate and the chromosome number is halved

Meiosis II - each of the sister chromatids separate to produce 4 haploid daughter cells

Question 16

What are the two ways that meiosis brings about genetic variation?

Answer 16

• independent segregation of homologous chromosomes

- crossing over which allows for new combinations of maternal and paternal alleles

Question 17

What are homologous chromosomes?

Answer 17

A pair of chromosomes where one is maternal and one is paternal that have the same gene loci (the same gene position)

Question 18

What is crossing over and what stage of meiosis does crossing over occur?

Answer 18

It occurs were the formation of chiasmata between chromatids in homologous pairs generate further genetic variation (check bio album)

Question 19

What are chiasmata?

Answer 19

The crossing over points between the sister and non sister chromatids of the maternal and paternal homologs to form bivalents when the homologous pairs are crossed over. (Check biology album)

Question 20

What is recombination?

Answer 20

Where the broken off portions of chromatid recombine with another chromatid in crossing over

Question 21

What are the steps in crossing over

Answer 21

1. The chromatids of each pair become twisted around each other
2. This causes tensions and so portions of chromatid break off
3. The broken portions then rejoin with the chromatids of its homologous partner ( usually the equivalent portions of homologous chromosomes are exchanged)
4. This causes new genetic combinations of maternal and paternal alleles to be produced

Question 22

What is independent segregation and what stage of meiosis does it occur at?

Answer 22

Where each homologous pair of chromosomes independently and randomly line up on the metaphase plate and so the combination of maternal and paternal chromosomes that go into the daughter cell of meiosis I is random allowing for a large number of possible combinations of chromosomes in the daughter cells. Basically it’s the variation in gametes from the different combinations of the maternal and paternal chromosomes.
Occurs during anaphase and metaphase I.

Question 23

How can you calculate the number of possible combinations of chromosomes for each daughter cell?

Answer 23

By doing 2^n where n is the number of pairs of homologous chronometer

Question 24

How can you calculate the possible combinations due to independent segregation and random fertilisation ( gametes)

Answer 24

By doing (2^n)^2 where n is the number of pairs of homologous chromosomes

Question 25

How is polyploidy and advantage in plants?

Answer 25

As it can cause bigger flowers and so bigger fruit and therefor more profit

Question 26

What can chromosome mutations lead to in humans and give 2 examples

Answer 26

It can lead to aneuploidy where there is either an extra chromosome of there is one chromosome missing e.g:

• trisomy 21 (Down’s syndrome)
• fragile X (turner’s syndrome)