sb3 genetics (paper 1)

Question 1

define gene

Answer 1

a section of DNA that codes for a single characteristic, e.g hair and eye colour

Question 2

what does DNA stand for

Answer 2

deoxyribonucleic acid

Question 3

define allele

Answer 3

a variation of the same genetic

Question 4

what are the two types of variation

Answer 4

environmental and genetic

Question 5

what is genetic variation (give examples)

Answer 5

characteristics inherited by your parents (blood type, eye colour, hair texture and colour)

Question 6

what is environmental variation (give examples)

Answer 6

characteristics you get from the environment around you (scars, hair length, piercings)

Question 7

give characteristics that could be both genetic and environmental

Answer 7

height, hair colour, skin colour

Question 8

what is a zygote

Answer 8

formed at fertilisation when a sperm and egg fuse

Question 9

how many chromosones does a zygote have

Answer 9

46

Question 10

how many pairs of chromosones does a zygote have

Answer 10

23

Question 11

how many chromosones does a sperm cell have

Answer 11

23

Question 12

how many chromosones does an egg cell have

Answer 12

23

Question 13

what is a recessive allele

Answer 13

a type of allele that needs two genes to express itself

Question 14

what is a dominant allele

Answer 14

a type of allele that only needs one gene to express itself

Question 15

what is homozygous

Answer 15

when the genotype letters are the same

Question 16

what is heterozygous

Answer 16

when the genotype letters are different

Question 17

state what is meant by the term genome

Answer 17

all of the DNA within the nucleus

Question 18

state what is meant by the term genotype

Answer 18

a letter to show the genetic code / allele

Question 19

state what is meant by the term phenotype

Answer 19

the physical characteristics of an organism

Question 20

describe the dna structure

Answer 20

• in a double helix
• sugar phosphate backbone
• made of complementary genetic bases

Question 21

name the four bases

Answer 21

• adenine (a)
• guanine (g)
• thymine (t)
• cytogine (c)

Question 22

in the dna structure, what is complementary to the base adenine?

Answer 22

thymine

Question 23

in the dna structure, what is complementary to the base guanine?

Answer 23

cytogine

Question 24

in the dna structure, what is complementary to the base thymine?

Answer 24

adenine

Question 25

in the dna structure, what is complementary to the base cytogine?

Answer 25

guanine

Question 26

what is a mutation

Answer 26

a random change in the genetic base

Question 27

draw the detailed DNA structure

Question 28

what is the purpose of mitosis

Answer 28

for growth and repair

Question 29

what is a gamete

Answer 29

a sex cell

Question 30

give examples of gametes

Answer 30

sperm, egg, pollen

Question 31

define haploid cells

Answer 31

cells with half the chromosones (23)

Question 32

define diploid cells

Answer 32

cells that have 46 chromosones

Question 33

what happens in asexual reproduction

Answer 33

- uses mitosis - no fusion of gametes - no mixing of genetic information - genetically identical - one parent

Question 34

what happens in sexual reproduction

Answer 34

- uses meiosis - mixing of genetic information - leads to a variety of offspring - two parents

Question 35

describe the stages of extracting DNA from fruit and the purpose of each step

Answer 35

- mash the fruit with salt water to seperate cells - sieve the mixture to get the fruit soup - add detergent to rupture the cell membrane - add protease enzyme to uncoil the DNA - slowly add ice cold ethanol to slow enzyme activity and make it insoluble (there will be a transparent layer ontop) - use a wooden stick/wire to extract the DNA

Question 36

advantages of sexual reproduction

Answer 36

- lots of variation - increases species survival due to the mixture of chromosones

Question 37

advantages of asexual reproduction

Answer 37

- very fast - doesn't require finding a mate - uses less energy

Question 38

disadvantages of sexual reproduction

Answer 38

- takes extremely long

Question 39

disadvantages of asexual reproduction

Answer 39

- doesn't have many variations

Question 40

what are the stages of meiosis

Answer 40

- prophase 1 - metaphase 1 - anaphase 1 - telophase 1 - prophase 2 - metaphase 2 - anaphase 2 - telophase 2

Question 41

(meiosis) what happens in prophase 1

Answer 41

- chromosones are condensed - they cross in same size and shape pairs to transfer genetic info

Question 42

(meiosis) what happens in metaphase 1

Answer 42

- chromosones are lined up in the middle

Question 43

(meiosis) what happens in anaphase 1

Answer 43

- spindle fibres pull apart the chromosones

Question 44

(meiosis) what happens in telophase 1

Answer 44

- cell is split into two

Question 45

(meiosis) what happens in prophase 2

Answer 45

- spindles and chromosones are formed in the two daughter cells formed from telophase 1

Question 46

(meiosis) what happens in metaphase 2

Answer 46

- chromosones are lined up in the middle

Question 47

(meiosis) what happens in anaphase 2

Answer 47

- chromosones are pulled away

Question 48

(meiosis) what happens in telophase 2

Answer 48

- cell is split into two (results in 4 daughter cells total)

Question 49

what is the purpose of protein synthesis

Answer 49

to make protein

Question 50

what are the two main processes in protein synthesis

Answer 50

transcription and translation

Question 51

what happens in transcription

Answer 51

- section of dna containing the gene to be transcripted unwinds - dna strands seperate - rna polymerase binds to non coding dna located infront of the gene - rna polymerase produces a complementary mrna strand from the coding dna of the gene (a and u, and c and g) - mrna leaves the nucleus - attatches to a ribosome - codons in the mrna code for specific amino acids

Question 52

what happens in translation

Answer 52

- transfer of amino acids to the ribosome by trna - anticodons on trna (match codons on mrna strands) - amino acids are linked to form polypeptides by peptide bonds - the order of bases in a section of dna decides the order of amino acids in the protein

Question 53

what blood type is recessive

Answer 53

o

Question 54

what four blood types are common in the abo system?

Answer 54

- type A, in which only the A antigen is present. - type B, in which only the B antigen is present. - type AB, in which both the A and B antigens are present. - type O, in which neither the A nor the B antigen is present.