Unit 2 AOS 1

Question 1

what are genes

Answer 1

sequences of bases located on chromosomes that code for specific proteins (ATCG)

Question 2

what do proteins from genes control

Answer 2

traits or characteristics of the organism

Question 3

what are alleles

Answer 3

different forms of a particular gene

Question 4

what is an example of a gene and a kind of allele

Answer 4

a gene would be eye colour and an allele of that gene is to have blue eyes

Question 5

what is a genome

Answer 5

the complete set of genetic instructions for an organism (the total DNA)

Question 6

how is a genome expressed

Answer 6

as the base sequence of the haploid set of chromosomes

Question 7

how many chromosomes in a human

Answer 7

46, 23 pairs

Question 8

how many autosomes in a human

Answer 8

44, 22 pairs

Question 9

how many sex chromosomes in a human

Answer 9

2,

Question 10

Where do your 46 chromosomes come from

Answer 10

23 from father, 23 from mother

Question 11

What are homologous chromosomes

Answer 11

matching pairs of chromosomes that have the same genes in the same places (same size)

Question 12

what is the loci

Answer 12

the position of the gene on a chromosome

Question 13

what is non-homologous

Answer 13

non-matching chromosomes

Question 14

what are the 2 types of chromosomes

Answer 14

sex chromosomes and autosomes

Question 15

how can autosomes be distinguished

Answer 15

the size, position of centromere and patterns of light and dark bands when stained

Question 16

what is a karyotype

Answer 16

an image of chromosomes from a cell arranged in an organised manner

Question 17

What do karyotypes do

Answer 17

allow us to see all the chromosomes and see if there is a wrong amount (diseases)

Question 18

What are the 3 chromosome abnormalities

Answer 18

changes in the number of chromosomes, changes in a part of a chromosome, changed arrangements of chromosomes

Question 19

what is trisomy

Answer 19

when an organism has an extra in a pair of chromosomes

Question 20

what it monosomy

Answer 20

when an organism has one chromosome in a pair

Question 21

what is a genotype

Answer 21

the combination of the particular alleles of a gene or genes that are present and active in a cell or in an organism

Question 22

what is a homozygous genotype

Answer 22

when a particular gene comprises of two identical alleles, eg AA or aa

Question 23

what is a heterozygous genotype

Answer 23

when a particular gene comprises of two different alleles, eg Aa

Question 24

what is a phenotype

Answer 24

A phenotype is the observable or measurable characteristics of an organism. It is a product of the genotype and the environment.

Question 25

what does codominance mean

Answer 25

when a heterozygote expresses both the dominant and the recessive trait of a gene in its phenotype

Question 26

what does codominance normally entail

Answer 26

showing both phenotypes or both colours (not mixed)

Question 27

what is incomplete dominance

Answer 27

appearance in a heterozygote of a trait that is between either of the trait’s homozygous phenotypes

Question 28

what does incomplete dominance entail

Answer 28

merging of phenotypes or colours together

Question 29

what are factors of a autosomal dominant trait (3)

Answer 29

both sexes are featured, all affected people have at least one affected parent, cant reappear after having 2 non affected people

Question 30

what are the factors of autosomal recessive traits (3)

Answer 30

trait can skip generations, parents that are not affected can have affected kids, if both parents are affected then all children will be as well,

Question 31

what are some features of X-linked dominant traits (3)

Answer 31

a male with the trait only passes it to all daughters, it disappears if no one is affected, in large pedigrees more females are affected

Question 32

what are some features of x linked recessive traits (3)

Answer 32

affected mothers have affected sons, daughters of affected fathers are carriers, across a large pedigree more males will be affected

Question 33

what is meiosis

Answer 33

sexual reproduction which halves the chromosome number to produce gametes

Question 34

what are the stages of meiosis

Answer 34

PMAT i PMAT ii

Question 35

what happens in interphase of meiosis

Answer 35

the DNA is replicated forming 4 chromosomes

Question 36

what happens in prophase i

Answer 36

the chromosomes condense and nuclear envelope degrades, starting crossing over

Question 37

what is crossing over (prophase i)

Answer 37

the chromosomes get tangled up and change/combine certain alleles that are random to cause genetic variation

Question 38

what happens in metaphase i

Answer 38

the new crossed over chromosomes line up down the equator of the cell

Question 39

what happens in anaphase i

Answer 39

the 4 chromosomes are separated by from each other when the spindle fibres pull them apart via the centromere

Question 40

what happens in telophase i

Answer 40

a nuclear envelope reforms around each new set of chromosomes (then cytokinesis occurs)

Question 41

what happens in prophase ii

Answer 41

chromosomes may re-condense again and the nuclear envelope breaks down again

Question 42

what happens in metaphase ii

Answer 42

the chromosomes line up down the equator of the cell

Question 43

what happens in anaphase ii

Answer 43

the chromosomes are spilt apart into single stranded ones by pulling from the spindle fibres on the sister chromatids

Question 44

what happens at telophase ii

Answer 44

a new envelope forms around each set of chromosomes

Question 45

at the end of meiosis how many haploid daughter cells are made

Answer 45

4 haploid daughter cells are made

Question 46

what are the causes of genetic variation

Answer 46

crossing over (prophase i) and independent assortment

Question 47

what is independent assortment

Answer 47

the formation of random chromosome combinations during meiosis that contributes towards producing variation