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GCSE - biology > B3 - genetics > Flashcards

B3 - genetics Flashcards

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1
Q

what is sexual reproduction

A

where genetic information from two organisms is combined to produce offspring that is genetically different to the parents

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2
Q

what is produced in meiosis

A

gametes

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3
Q

what are gametes

A

reproductive cells:
sperm and egg cells (ova) in animals
egg cells and pollen in plants

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4
Q

chromosomes in gametes

A

gametes are haploid
contain half the number of chromosomes than normal cells
(23 in humans)

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5
Q

what occurs during fertilisation

A

male and female gametes fuse to form a zygote

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6
Q

chromosomes in a zygote

A

diploid: contains full set of chromosomes, half from mother, half from father
(46/ 23 pairs in humans)

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7
Q

what is meiosis

A

a type of cell division

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8
Q

properties of meiosis (4)

A
  • produces genetically different cells
  • produces 4 different haploid daughter cells
  • forms gametes
  • happens in testes/ ovaries
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9
Q

how many divisions are there in meiosis

A

two

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10
Q

meiosis: division 1 (4)

A
  • diploid cell duplicates DNA to produce 46 pairs (92 single) of chromosomes
  • chromosomes pairs line up in pairs in centre: 1 from mum, 1 from dad
  • pairs are pulled apart, each daughter cell only has 1 copy of each pair (random whether from mum of dad)
  • results in 2 genetically different DIPLOID cells
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11
Q

meiosis: division 2

A
  • chromosome line up along centre of cell
  • pairs are pulled apart (become chromatids)
  • results in 4 HAPLOID daughter cells, each is genetically different
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12
Q

why are haploid gametes needed for sexual reproduction

A

in order to fuse with opposite gamete to create a DIPLOID zygote that’ll have the correct full set of chromosomes

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13
Q

what is an organism’s geneome

A

All the genetic information an organism has

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14
Q

where are genes found

A

genes are a section of DNA, found on a chromosome

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15
Q

function of genes

A

they code for a particular sequence of amino acids , to make a specific protein

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16
Q

what determines what protein is produced (due to genes)

A

the sequence of bases in the gene

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17
Q

where is DNA found in eukaryotic cells

A

in chromosomes, within the nucleus of eukaryotic cells

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18
Q

what are the bases of DNA

A

A - adenine
T - thymine
C - cytosine
G - guanine

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19
Q

what are the base pairs in DNA

A

A and T
C and G

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20
Q

what is it called when the bases pair together

A

complementary base pairing

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21
Q

how are the complementary base pairs joined together

A

weak hydrogen bonds

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22
Q

what is DNA

A

deoxyribonucleic acid:
strands of polymers made up of repeating units called nucleotides

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23
Q

what do nucleotides consist of

A

one sugar molecule
one phosphate molecule
one base

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24
Q

what forms the backbone of DNA

A

the sugar and phosphate molecules in the nucleotides (they alternate)

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25
Q

shape of DNA

A

two strands coiled together in a double helix

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26
Q

what are alleles

A

different versions of the same gene

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27
Q

what do genes control

A

the characteristics you develop, different genes control different characteristics

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28
Q

how many alleles of each gene is in the body

A

two - one on each chromosome in a pair (one from mum, one from dad)

29
Q

define homozygous

A

when an organism has two alleles for a particular gene that are the same

30
Q

define heterozygous

A

when an organism has two alleles for a particular gene that are different

31
Q

what are the two types of allele

A

dominant and recessive

32
Q

what is a dominant allele

A

always expressed, even if only one copy is present, they overrule recessive alleles

33
Q

what is a recessive allele

A

a type of allele that when present on its own will not affect the individual. Two copies of the allele need to be present for the phenotype to be expressed

34
Q

how are dominant and recessive alleles expressed on genetic diagrams

A

dominant - capital letters
recessive - lowercase letters

35
Q

what is a genotype

A

the combination of alleles you have including the two alleles a person has inherited for a particular gene (even if recessive)

36
Q

what is a phenotype

A

the physical characteristics of an organism

37
Q

what is monohybrid inheritance

A

the inheritance of characteristics controlled by a single gene

38
Q

how many matched pairs of chromosomes do human body cells have

A

23

39
Q

which pair of chromosomes determine sex

A

the 23rd pair

40
Q

which chromosome pattern determines each sex

A

female - XX
male - XY

41
Q

which gamete determines sex

A

sperm - carries both X and Y, ova only carries X

42
Q

what does sex determination in humans depend on

A

whether the sprem that fertilises the egg carries an X or Y chromosome

43
Q

what are the different types of variation

A

environmental and genetic

44
Q

what is genetic variation cause by

A

the different alleles an organism has

45
Q

examples of genetic variation

A

eye colour, natural hair colour, nose shape

46
Q

what is environmental variation

A

characteristics that an organism acquires after birth (during their lifetimes)

47
Q

examples of environmental variation

A

pericings, tattoos, hair colour (if dyed), hair length

48
Q

examples of variation that are a mixture of environment and genetic

A

height
weight

49
Q

what is continuous variation

A

a characteristic that changes gradually over a range of values eg. height, weight

50
Q

what is discontinuous variation

A

when there are distinct differences for a characteristic which have a limited number of possible values eg. eye colour, blood group

51
Q

what is a mutation

A

a change to the base sequence of DNA

52
Q

what is a characteristic controlled by multiple genes called

A

a polygenic trait

53
Q

examples of characteristics controlled by multiple genes

A

hair colour, eye colour, height (physical structures)

54
Q

where do mutations occur, and what do they result in

A

within a gene, result in: an allele or a different version of the gene

55
Q

what are some causes of genetic variation

A

sexual reproduction and mutation

56
Q

what is the result of most mutations

A

they have little-no effect on the phenotype

57
Q

examples of a mutation having a small effect

A

hamsters having long hair instead of short hair

58
Q

how may some mutations have big effects on the phenotype

A

may result in the production of a protein so different, that it can no longer carry out its function

59
Q

examples of a mutation having a big effect

A

cystic fibrosis

60
Q

why do many mutations have no effect on the phenotype

A

the mutation may occur in a section of DNA with no function, or it may occur in a protein-coding region, but not affect the amino acid sequence of the protein.

61
Q

how does a mutation cause cystic fibrosis

A
  • causes a protein that controls the movement of salt and water in and out of cells to stop working properly
  • leads to the production of thick mucus in the lungs and digestive system
  • makes it difficult to breath and digest food
62
Q

how may sunlight/ UV cause skin cancer

A

can cause mutations in cells that cause them to multiply uncontrollably forming a tumor that may invade neighbouring tissues

63
Q

how may mutation cause variation

A
  • mutations can be inherited, passed on from one individual to another
  • If a mutation causes a new phenotype that makes an organisms better suited to a particular environment, it can lead to rapid change in the characteristics of the individuals in that species.
64
Q

info about the human genome project

A
  • started in 1990
  • mapped the locations of around 20500 genes
  • completed in 2003
65
Q

what was the human genome project

A

scientists created a complete map of the human genome

66
Q

how many genes related to disease did the human genome project help identify

A

1800 genes

67
Q

benefits of the human genome project (3)

A
  • prediction and prevention of disease
  • testing and treatment for inherited disorders
  • new and better medicines
68
Q

drawbacks of genetically modified treatments/ knowing what diseases people may contract

A
  • stress: if someone knows they may get a major disease, they might constantly live in stress of it even if they never actually contract it
  • gene-ism: people with genetic disorders may be pressured to not have children
  • discrimination: if someone has a genetic likelihood of a serious disease they may not be able to get life insurance (or itll be expensive) and employers may discriminate against them

GCSE - biology (9 decks)

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