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gcse biology > sb3 genetics (paper 1) > Flashcards

sb3 genetics (paper 1) Flashcards

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1
Q

define gene

A

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

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2
Q

what does DNA stand for

A

deoxyribonucleic acid

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3
Q

define allele

A

a variation of the same genetic

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4
Q

what are the two types of variation

A

environmental and genetic

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5
Q

what is genetic variation (give examples)

A

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

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6
Q

what is environmental variation (give examples)

A

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

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7
Q

give characteristics that could be both genetic and environmental

A

height, hair colour, skin colour

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8
Q

what is a zygote

A

formed at fertilisation when a sperm and egg fuse

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9
Q

how many chromosones does a zygote have

A

46

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10
Q

how many pairs of chromosones does a zygote have

A

23

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11
Q

how many chromosones does a sperm cell have

A

23

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12
Q

how many chromosones does an egg cell have

A

23

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13
Q

what is a recessive allele

A

a type of allele that needs two genes to express itself

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14
Q

what is a dominant allele

A

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

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15
Q

what is homozygous

A

when the genotype letters are the same

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16
Q

what is heterozygous

A

when the genotype letters are different

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17
Q

state what is meant by the term genome

A

all of the DNA within the nucleus

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18
Q

state what is meant by the term genotype

A

a letter to show the genetic code / allele

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19
Q

state what is meant by the term phenotype

A

the physical characteristics of an organism

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20
Q

describe the dna structure

A
  • in a double helix
  • sugar phosphate backbone
  • made of complementary genetic bases
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21
Q

name the four bases

A
  • adenine (a)
  • guanine (g)
  • thymine (t)
  • cytogine (c)
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22
Q

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

A

thymine

23
Q

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

A

cytogine

24
Q

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

A

adenine

25
Q

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

A

guanine

26
Q

what is a mutation

A

a random change in the genetic base

27
Q

draw the detailed DNA structure

A
28
Q

what is the purpose of mitosis

A

for growth and repair

29
Q

what is a gamete

A

a sex cell

30
Q

give examples of gametes

A

sperm, egg, pollen

31
Q

define haploid cells

A

cells with half the chromosones (23)

32
Q

define diploid cells

A

cells that have 46 chromosones

33
Q

what happens in asexual reproduction

A
  • uses mitosis
  • no fusion of gametes
  • no mixing of genetic information
  • genetically identical
  • one parent
34
Q

what happens in sexual reproduction

A
  • uses meiosis
  • mixing of genetic information
  • leads to a variety of offspring
  • two parents
35
Q

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

A
  • 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
36
Q

advantages of sexual reproduction

A
  • lots of variation
  • increases species survival due to the mixture of chromosones
37
Q

advantages of asexual reproduction

A
  • very fast
  • doesn’t require finding a mate
  • uses less energy
38
Q

disadvantages of sexual reproduction

A
  • takes extremely long
39
Q

disadvantages of asexual reproduction

A
  • doesn’t have many variations
40
Q

what are the stages of meiosis

A
  • prophase 1
  • metaphase 1
  • anaphase 1
  • telophase 1
  • prophase 2
  • metaphase 2
  • anaphase 2
  • telophase 2
41
Q

(meiosis) what happens in prophase 1

A
  • chromosones are condensed
  • they cross in same size and shape pairs to transfer genetic info
42
Q

(meiosis) what happens in metaphase 1

A
  • chromosones are lined up in the middle
43
Q

(meiosis) what happens in anaphase 1

A
  • spindle fibres pull apart the chromosones
44
Q

(meiosis) what happens in telophase 1

A
  • cell is split into two
45
Q

(meiosis) what happens in prophase 2

A
  • spindles and chromosones are formed in the two daughter cells formed from telophase 1
46
Q

(meiosis) what happens in metaphase 2

A
  • chromosones are lined up in the middle
47
Q

(meiosis) what happens in anaphase 2

A
  • chromosones are pulled away
48
Q

(meiosis) what happens in telophase 2

A
  • cell is split into two (results in 4 daughter cells total)
49
Q

what is the purpose of protein synthesis

A

to make protein

50
Q

what are the two main processes in protein synthesis

A

transcription and translation

51
Q

what happens in transcription

A
  • 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
52
Q

what happens in translation

A
  • 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
53
Q

what blood type is recessive

A

o

54
Q

what four blood types are common in the abo system?

A
  • 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.

gcse biology (10 decks)

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