Topic 4 - B : Diversity and selection

Question 1

Diploid

Answer 1

each cell has two of each chromosome
one from mum and one from dad
each chromosome has same genes, but different alleles
matching chromosome pairs are called homologous pairs

Question 2

Gametes

Answer 2

have haploid number of chromosomes (one number of each)
two gametes=zygote

Question 3

Meiosis

Answer 3

-DNA unravels and replicates so there are two copies of each chromosome called chromatids
-DNA condenses to form x shaped chromosomes made of two sister chromatids joined by centromere (P1)
-Chromosomes arranged into homologous pairs and then separated
-Meiosis II -sister chromatids making up each chromosome are separated.
-four haploid cells that are genetically different

Question 4

Crossing over

Answer 4

During meiosis I
chromatids twist around each other and bits of chromatids swap over
still contain same genes but different combination

Homologous arrange themselves into pairs
chromatids cross over

Question 5

independent segregation

Answer 5

When homolougous pairs are seperated in meiosis , its completely random which chromosome from each pair ends up in which daughter cell.
Four daughter cells have completely different combinations.
this is independent segragation ( shuffling of chromosomes leading to genetic variation in potential offspring

Question 6

Define mutation

Answer 6

change in DNA base pair sequence

Question 7

degenerate

Answer 7

more possible combinations of bases than amino acids

Question 8

What is the difference between substitution mutations and deletion

Answer 8

substitution won’t always lead to changes, but deletion will change the number of bases, causing a shift in all base triplets in all the base triplets after it.

Question 9

What can increase chances of mutations

Answer 9

radiation
chemicals
viruses

Question 10

chromosome mutations

Answer 10

meiosis isn’t carried out correctly and some cells have wrong numbers of chromosomes

Question 11

Genetic diversity

Answer 11

number of different alleles of genes in a population

Question 12

Genetic bottlenecks

Answer 12

event that causes a big reduction in a population

Question 13

Founder effect

Answer 13

happens when just a few organisms from a population start a new colony with only a small number of different alleles in the initial gene pool.

Question 14

Natural selection

Answer 14

-individuals that have an allele that increases their chance of survival are more likely to survive and reproduce
-greater proportion of next generation inherits the beneficial allele
-more likely to survive and pass on alleles
-frequency of beneficial allele increases over generations
-leads to evolution as advantageous alleles become more common in the population

Question 15

behavioural adaption

Answer 15

ways an organism acts that increase its chance of survival

Question 16

physiological adaptions

Answer 16

processes in an organisms body that increase chance of survival

Question 17

Anatomical adaptions

Answer 17

structural features of organisms body that increase its chance of survival

Question 18

Directional selection

Answer 18

where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.

Question 19

Stabilising selection

Answer 19

where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce