Genetic Diversity and Adaptation

Question 1

Define exon

Answer 1

Triplet sequence coding for polypeptide

Question 2

How to make dilution series in liquid culture of bacteria

Answer 2

• Add 1 part bacteria culture to 9 parts sterile liquid to make 10^–1 dilution
• Mix
• Repeat using 9 parts fresh sterile liquid and 1 part of previous dilution to make new dilution

Question 3

How to work out original cells in colony

Answer 3

Number of colonies x dilution factor

Question 4

What happens if dilution is too low?

Answer 4

• count is more unlikely to be accurate
• because cells will be overlapping

Question 5

Why is antibiotic resistance more likely to occur? (3)

Answer 5

• used more often so resistant gene more likely to pass on gene for resistance
• high frequency of mutations for resistance so gene passed on more
• antibiotic used for longer so more chance for mutation

Question 6

What is diploid

Answer 6

A cell where the nucleus contains two sets of chromosomes

Question 7

How does meiosis create genetic variation (2)

Answer 7

• crossing over
• independent segregation

Question 8

Gene mutation?

Answer 8

Change in sequences of bases in DNA

Question 9

Outcomes of meiosis (3)

Answer 9

• 4 daughter cells
• genetically different cells
• half the number of chromosome as parent cells

Question 10

Define gene

Answer 10

A section of DNA that codes for making a polypeptide and functional RNA.

Question 11

Define locus

Answer 11

Location of a particular gene on a chromosome

Question 12

Define allele

Answer 12

Number of alternative forms of a gene

Question 13

What is an homologous chromosomes

Answer 13

Pair of chromosomes that have the same genes but may have different alleles

Question 14

Define degenerate

Answer 14

Each amino acid is coded for by more than one triplet of bases

Question 15

Define universal

Answer 15

same triplet of bases code for the same amino acids in all organisms

Question 16

define non overlapping

Answer 16

each base in a gene is only part of one triplet that codes for an amino acid

Question 17

Describe transcription

Answer 17

• DNA helices unwinds and separates DNA strands breaking hydrogen bonds
• Each DNA strand acts as a template
• Free mRNA nucleotides attach to the complimentary DNA base
• Adenine to uracil and guanine to cytosine
• RNA polymerase joins the mRNA nucleotides creating phosphodiester bonds between adjacent nucleotides
• pre-mRNA spliced to form mRNA

Question 18

Describe translation

Answer 18

• mRNA binds to ribosomes to read start codon
• Each ribosome has two binding sites
• tRNA anticodon carrying specific amino acids bind to complimentary mRNA codon
• Peptide bonds formed between amino acids with energy from ATP
• Ribosome moves along codon releasing tRNA
• Ribosome stops when reached stop codon
• Polypeptide released to the rough endoplasmic reticulum

Question 19

What does meiosis create

Answer 19

4 genetically different haploid cell

Question 20

What is independent segregation

Answer 20

maternal and paternal chromosomes reshuffled in any order down the equator
- Produces new combination of alleles

Question 21

what is crossing over

Answer 21

• homologous chromosomes associate (bivalent forms)
• chiasma form (chromosomes entangle)
• equal lengths of non-sister chromatids are exchanged
• Producing new combination of alleles

Question 22

Describe natural selection

Answer 22

• New allele for a gene are created by random mutations
• If the new allele increase the chance of survival in that environment they are more likely to reproduce
• They pass on the advantageous allele to the next generation
• Over generation the new allele frequency increases

Question 23

What is directional selection

Answer 23

• one extreme trait has selected advantage
• occurs when change in environment

Question 24

what is stabilising selection

Answer 24

• Modal trait has selected advantage
• Occurs when no change in environment