Genetic diversity

Question 1

What is a gene mutation

Answer 1

a change in the base sequence of DNA

Question 2

Types of gene mutation

Answer 2

substitution

deletion

Question 3

What is a substitution mutation and how will affect an organism

Answer 3

a single swap of one base for another

a change in the primary and therefore tertiary structure so can affect the protein structure and function

Question 4

Why might a substitution mutation not affect the amino acid sequence

Answer 4

As the genetic code is degenerate, so the base that is swapped will still cause the codon to code for the same amino acid

Question 5

What is a deletion mutation and what effect can it have on the amino acid sequence

Answer 5

a deletion of a single base in a DNA sequence
which will cause a frameshift

will have a large impact on amino acid sequence as lots of the codons can be affected

so different amino acids are encoded

Question 6

What is chromosomal mutation and what can 3 things can it result in

Answer 6

a mutation in the number of chromosomes by chromosome non disjunction in meiosis

trisomy (extra copy of chromosome)

aneuploidy (missing copy of a chromosome)

polyploidy (whole extra set of chromosomes)

Question 7

describe meiosois

Answer 7

A form of cell division that produces 4 daughter cells that are genetically different from each other

involves 2 separate divisions

haploid cells are formed from diploid cells

produces gametes

Question 8

Overall aim of meiosis I and II

Answer 8

I - homologous chromosomes separate

I - sister chromatids separate

Question 9

What is the process of crossing over

Answer 9

Occurs during prophase I

homologous chromosomes pair to form bivalents

sections of chromatids break and exchange with chromatids on homologous chromosome

chromosomes will now contain recombinant alleles

Question 10

Describe how independent segregation leads to variation in meiosis

Answer 10

Homologous chromosomes line up at the equator randomly

therefore chromosomes separate randomly

so gametes will have different combinations of maternal and paternal chromosomes

Question 11

3 causes of variation in meiosis and after

Answer 11

Crossing over

independent segregation

random fertilisation

Question 12

What does genetic diversity mean

Answer 12

number of different alleles of genes in a population

Question 13

What is an allele

Answer 13

a variation of a gene

Question 14

What is natural selection and the steps

Answer 14

leads to evolution of population

random mutation can result in new alleles of a gene

new allele can be advantageous in certain environments, so possessor of allele is more likely to survive and reproduce

offspring will inherit the advantageous allele

over many generations, the new allele increases in frequency in the population

Question 15

3 types of adaptations

Answer 15

anatomical

physiological

behavioural

Question 16

3 types of natural selection

Answer 16

directional

stabilising

disruptive

Question 17

what is directional selection

Answer 17

the favour of one extreme phenotype, normal distribution curve shifts in the direction of this phenotype

Question 18

How do bacteria become resistant to antibiotics

Answer 18

Random mutation creates a resistance allele in bacterial population

when exposed to the antibiotic, only those with the resistant allele will survive and reproduce

resistance allele frequency increases over generation

Question 19

What is stabilising selection

Answer 19

the favour of the average phenotype

causes variation of traits to decrease over generations

normal distribution curve will become narrower

Question 20

How is variation in birth weight decreased

Answer 20

The average birth weight has a selective advantage

more likely to survive and reproduce to pass allele to offspring