Diversity and Selection (Topic 4B)

Question 1

diploid number in abbreviated to…

Answer 1

2n

Question 2

how many chromosomes does a diploid cell have?

Answer 2

two of each chromosome - one from each parent

Question 3

pairs of matching chromosomes are called…

Answer 3

homologous pairs

Question 4

what type of cell are gametes?

Answer 4

haploid

Question 5

haploid number is abbreviated to….

Answer 5

n

Question 6

how many chromosomes does a haploid cell have?

Answer 6

one copy of each chromosome in a homologous pair

Question 7

what is the haploid number for humans?

Answer 7

23

Question 8

when gametes fuse during reproduction they form a…

Answer 8

zygote

Question 9

meiosis starts with _____ cells and produces _____ cells

Answer 9

diploid
haploid

Question 10

meiosis produces…

Answer 10

gametes

Question 11

before meiosis can occur what 2 steps have to happen?

Answer 11

DNA unravels and replicates so there are two copies of each chromosome, called chromatids

DNA condenses to form sister chromatids joined by a centromere

Question 12

what happens in MEIOSIS I?

Answer 12

the chromosomes arrange themselves into homologous pairs that are then seperated, halving the chromosome number

Question 13

after MEIOSIS I occurs what happens next?

Answer 13

MEIOSIS II

Question 14

what happens in MEIOSIS II?

Answer 14

the pairs of sister chromatids are seperated. 4 genetically different haploid cells are produced

Question 15

what two events occur during meiosis that lead to genetic variation?

Answer 15

1. crossing over of chromatids
2. independent segregation of chromosomes

Question 16

what is crossing over of chromatids?

Answer 16

the chromatids twist around each other and bits of chromatids swap over

Question 17

what is independent segregation of chromosomes?

Answer 17

homologous pairs are separated at random in MEIOSIS I so the daughter cells produced have completely different maternal and paternal combinations of chromosomes

Question 18

what is a substitution mutation?

Answer 18

one base is substituted with another

Question 19

what is a deletion mutation?

Answer 19

one base is deleted

Question 20

the order of DNA bases in a gene determines the…

Answer 20

order of amino acids in a protein

Question 21

why won’t all substitution mutations end up causing a change in the amino acid sequence?

Answer 21

genetic code is degenerate so some amino acids are coded for by more than one triplet so the same amino acid may be expressed still

Question 22

why will a base deletion always cause a different amino acid to be produced?

Answer 22

a deletion changes the number of bases present which causes a shift in all base triplets after it

Question 23

what are mutagenic agents?

Answer 23

something that increases the probability of a mutation occuring

Question 24

what is chromosome disjunction?

Answer 24

a chromosome mutation where the chromosomes fail to separate properly

Question 25

genetic diversity is…

Answer 25

the number of different alleles of genes in a species or population

Question 26

genetic diversity in a population is increased by…

Answer 26

1. mutations in DNA forming new alleles
2. gene flow

Question 27

gene flow is….
caused by…

Answer 27

when different alleles are introduced into a population
caused by individuals from another population migrate into it and reproduce

Question 28

a genetic bottleneck is…

Answer 28

an event which causes a big reduction in population

Question 29

what effect does a genetic bottleneck have on a population?

Answer 29

reduces the number of different alleles in the gene pool, reducing genetic diversity

Question 30

describe the process of natural selection

Answer 30

1. in a population some individuals have an advantageous allele that increases their chance of survival so are more likely to survive and reproduce, passing on the allele
2. so a greater proportion of the next generation have this allele
3. they in turn are more likely to survive and pass on the allele
4. frequency of the allele in the population increases each generation
5. this leads to evolution as the allele becomes more common in the population

Question 31

what are the three types of adaption an animal can do to increase its chance of survival?

Answer 31

behavioral
physiological
anatomical

Question 32

what is a behavioral adaption?

Answer 32

the way an organism acts that increases its chance of survival

Question 33

what is a physiological adaption?

Answer 33

processes inside the organisms body which increase their chance of survival

Question 34

what is an anatomical adaption?

Answer 34

structural features of an organisms body that increases its chance of survival

Question 35

directional selection works against ___ of the _____ in a range of ____

Answer 35

one
extremes
phenotypes

Question 36

directional selection results in…

Answer 36

one phenotype becoming rare and another becoming common

Question 37

stabilising selection works against ___ _____ in a range of ____

Answer 37

both extremes in a range of phenotypes

Question 38

stabilising selection results in…

Answer 38

variation about the mode being reduced

Question 39

disruptive selection is when…

Answer 39

extremes at both ends of the phenotype are favoured

Question 40

disruptive selection results in…

Answer 40

two or more different species forming

Question 41

what is an inhibition zone?

Answer 41

a patch where bacteria cannot grow on the agar

Question 42

the size of an inhibition zone tells you…

Answer 42

how well an antibiotic works