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GCSE - biology > B3 - genetics > Flashcards

B3 - genetics Flashcards

(68 cards)

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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
shape of DNA
two strands coiled together in a double helix
26
what are alleles
different versions of the same gene
27
what do genes control
the characteristics you develop, different genes control different characteristics
28
how many alleles of each gene is in the body
two - one on each chromosome in a pair (one from mum, one from dad)
29
define homozygous
when an organism has two alleles for a particular gene that are the same
30
define heterozygous
when an organism has two alleles for a particular gene that are different
31
what are the two types of allele
dominant and recessive
32
what is a dominant allele
always expressed, even if only one copy is present, they overrule recessive alleles
33
what is a recessive allele
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
how are dominant and recessive alleles expressed on genetic diagrams
dominant - capital letters recessive - lowercase letters
35
what is a genotype
the combination of alleles you have including the two alleles a person has inherited for a particular gene (even if recessive)
36
what is a phenotype
the physical characteristics of an organism
37
what is monohybrid inheritance
the inheritance of characteristics controlled by a single gene
38
how many matched pairs of chromosomes do human body cells have
23
39
which pair of chromosomes determine sex
the 23rd pair
40
which chromosome pattern determines each sex
female - XX male - XY
41
which gamete determines sex
sperm - carries both X and Y, ova only carries X
42
what does sex determination in humans depend on
whether the sprem that fertilises the egg carries an X or Y chromosome
43
what are the different types of variation
environmental and genetic
44
what is genetic variation cause by
the different alleles an organism has
45
examples of genetic variation
eye colour, natural hair colour, nose shape
46
what is environmental variation
characteristics that an organism acquires after birth (during their lifetimes)
47
examples of environmental variation
pericings, tattoos, hair colour (if dyed), hair length
48
examples of variation that are a mixture of environment and genetic
height weight
49
what is continuous variation
a characteristic that changes gradually over a range of values eg. height, weight
50
what is discontinuous variation
when there are distinct differences for a characteristic which have a limited number of possible values eg. eye colour, blood group
51
what is a mutation
a change to the base sequence of DNA
52
what is a characteristic controlled by multiple genes called
a polygenic trait
53
examples of characteristics controlled by multiple genes
hair colour, eye colour, height (physical structures)
54
where do mutations occur, and what do they result in
within a gene, result in: an allele or a different version of the gene
55
what are some causes of genetic variation
sexual reproduction and mutation
56
what is the result of most mutations
they have little-no effect on the phenotype
57
examples of a mutation having a small effect
hamsters having long hair instead of short hair
58
how may some mutations have big effects on the phenotype
may result in the production of a protein so different, that it can no longer carry out its function
59
examples of a mutation having a big effect
cystic fibrosis
60
why do many mutations have no effect on the phenotype
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
how does a mutation cause cystic fibrosis
- 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
how may sunlight/ UV cause skin cancer
can cause mutations in cells that cause them to multiply uncontrollably forming a tumor that may invade neighbouring tissues
63
how may mutation cause variation
- 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
info about the human genome project
- started in 1990 - mapped the locations of around 20500 genes - completed in 2003
65
what was the human genome project
scientists created a complete map of the human genome
66
how many genes related to disease did the human genome project help identify
1800 genes
67
benefits of the human genome project (3)
- prediction and prevention of disease - testing and treatment for inherited disorders - new and better medicines
68
drawbacks of genetically modified treatments/ knowing what diseases people may contract
- 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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