genetics and meiosis

Question 1

meiosis

Answer 1

nuclear division that produces 4 haploid cells from a diploid cell. The gametes are used in sexual reproduction.

Question 2

4 things in prophase I

Answer 2

1 Chromosomes condense and become visible
2 crossing over occurs
3 centrioles migrate to opposite poles forming spindle fibre
4 nuclear envelope breaks down and nucleolus disappears

Question 3

chromosomes of bivalents are joined at the

Answer 3

chiasmata

Question 4

2 things in metaphase I

Answer 4

1. homologous pairs chromosomes are arranged randomly on equator
   2 homologous chromosomes are still attached at chiasmata

Question 5

1 thing in anaphase I

Answer 5

spindle fibres attached at centromeres contract and pull homologous chromosomes apart- one pair to each pole

Question 6

telophase I

Answer 6

1 spindle fibres break down
2 chromsones uncoil
3 in animals nuclear envelope and nucleolus reform

Question 7

what is the division after anaphase I called

Answer 7

reduction division

Question 8

cytokinesis is animals

Answer 8

organelles distributed
cell surface membrane pinches inwards creating cleavage furrow which contracts

Question 9

cytokinesis in plants

Answer 9

organelles distributed
vesicles form Golgi apparatus gather along the equator of spindle and merge to create new cell membrane

Question 10

prophase II

Answer 10

nucleolus and nuclear envelop disappear, centriole move to opposite poles, chromosomes condense

Question 11

metaphase II

Answer 11

chromosomes arrange themselves on equator. Spindle fibres attach to centromere of each chromosome

Question 12

crossing over

Answer 12

the exchange of alleles between non sister chromatids of homologous chromosomes

Question 12

anaphase II

Answer 12

centromeres divide and are pulled by spindle fibre to opposite poles carrying chromatids with them. Chromatids are separated

Question 13

locus

Answer 13

position of gene on chromosome

Question 14

gene 3 marks

Answer 14

a specific sequence of DNA occupying a position on a chromosome that codes for a specific protein, Each gene consists. of 2 or more alleles

Question 15

phenotype

Answer 15

observable features of an organisms determined by its genes and environment

Question 16

genotype

Answer 16

alleles an organism has

Question 17

homozygous

Answer 17

having 2 identical alleles of a gene BB/bb

Question 18

dominant allele

Answer 18

has the same effect on a phenotype whether or not another allele is present

Question 19

co dominance

Answer 19

co dominant alleles each effect phenotype when both are present

Question 20

multiple allele

Answer 20

the existence of 3 or more alleles of a gene eg blood groups

Question 21

sex linkage

Answer 21

genes or alleles present in sex chromosomes are inherited together

Question 22

sources of genetic mutation meiosis

Answer 22

crossing over-new combination of alleles on the 2 chromosomes
independent assortment- different combination of alleles in daughter cells due to random alignment of homologous Paris along the equator of the spindle
fusion of gametes- at fertilisation there is a random fusion of gametes creating variation between zygotes

Question 23

crossing over is more likely to occur

Answer 23

further down the chromosomes away from the centromere

Question 24

work out the number of possible chromosomes combinations

Answer 24

2^n where n is the number of chromosomes in a haploid cell 23 in humans

Question 25

chi squared is used to

Answer 25

find the difference between expected and observed results

Question 26

if chi squared value is bigger than critical value then

Answer 26

differences are due to chance otherwise differences are significant and caused by something else

Question 27

haploid

Answer 27

containing one complete set of chromosomes

Question 28

diploid

Answer 28

containing two complete set of chromosomes

Question 29

need for reductive division

Answer 29

reduces number of chromosomes to half original number diploid to haploid so when gametes fuse cell with have correct number of chromosomes

Question 30

homologous pair of chromosomes

Answer 30

2 chromosomes with similar gene loci but different alleles- one inherited form each parent

Question 31

allele

Answer 31

alternative form of a gene

Question 32

F1

Answer 32

first generation of offspring from a genetic cross

Question 33

F2

Answer 33

the offspring produced when F1 individuals reproduce with one another

Question 34

autosomal linkage

Answer 34

the presence of 2 genes on the same autosome, tend to b'e inherited together and do not assort independently

Question 35

why is haemophilia only found in men

Answer 35

factor vII is a gene found on t a non-homologous region of the x chromosome, Males (xy) only have one copy of the allele to be diseasedwhereas females (xx) have 2.

Question 36

epistasis

Answer 36

interaction of 2 different genes at different loci- one gene may effect expression of another

Question 37

continuous variation

Answer 37

variation within a range eg- mass and height

Question 38

what is variation

Answer 38

differences amongst individuals of the same species

Question 39

what is variation caused by

Answer 39

genes and environment

Question 40

what is genetic variation caused by (5)

Answer 40

1 independent assortment of chromosomes during mitosis 2 crossing over between non sister chromatids of homologous chromosomes during meiosis 3 random mating between organisms within species 4 random fertilisation of gametes 5 mutation

Question 41

discontinuous variation

Answer 41

can only take particular values eg gender and shoe size

Question 42

monogenic

Answer 42

characteristics influenced by only one gene

Question 43

natural selection

Answer 43

process in which fitter individuals who are better adapted to the environment survive and pass on the advantageous genes to future generations

Question 44

evolution

Answer 44

process by which the frequency of alleles in the gene pool change over time

Question 45

genetic drift

Answer 45

small change in alleles frequency occurs as a result of the fact not all the individuals in a population reproduce. effect amplified in very small groups isolated forms eh rest of the population

Question 46

genetic bottleneck effect

Answer 46

rapid reduction of population size which has an effect on genetic variation in future generations

Question 47

founder effect

Answer 47

decrease in genetic diversity which occurs when the population descends from a small number of ancestors

Question 48

selection

Answer 48

process by which organisms that are better adapted to the environment survive and breed while those less well adapted do not

Question 49

speciation

Answer 49

process by which new species arise after a population becomes seperated and cannot interbreed

Question 50

antibiotic resistance

Answer 50

1 random mutation occurs in bacteria 2 mutation bacteria can survive and reproduce 3 they pass mutant allele over many generations

Question 51

3 ways natural selection can act on a population

Answer 51

directional selection against an extremes stabilising selection against both extremes disruptive selection against the mean

Question 52

species

Answer 52

populations of similar organisms with similar morphological and physical features occupying the same niche and can reproduce to make fertile offspring. Reproductively isolated from other populations

Question 53

allele frequency

Answer 53

relative proportions of alleles of a gene present in a population

Question 54

3 causes of allele frequency change in a population

Answer 54

mutation, migration, natural selection

Question 55

hardy Wienberg principle in words

Answer 55

in a large randomly mating population there is a fixed relationship between gene and genotype frequency. Frequencies remain constant unless there is mutation, migration or natural selection