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Biology GCSE > Topic 3 - Genetics > Flashcards

Topic 3 - Genetics Flashcards

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1
Q

asexual reproduction

A

reproducing without fertilisation and produces genetically identical offspring

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2
Q

vertebrate

A

animal that has a backbone and a skeleton

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3
Q

sexual reproduction

A

reproducing using two parents and produces offspring its characteristics from both parents

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4
Q

what is DNA

A

contains instructions for an organism

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5
Q

genome

A

the entire set of DNA instructions found in a cell - in humans, the genome consists of 23 pairs of chromosomes located in the cell’s nucleus

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6
Q

chromosome

A

thread-like structures located inside the nucleus of animal and plant cells; each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA) - one DNA molecule contains two strands of DNA

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7
Q

gene

A

a particular sequence of bases that codes for a protien

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8
Q

polymer

A

substances composed of smaller ‘blocks’ composed together

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9
Q

monomer

A

atoms or small molecules that bond together to form more complex structures such as polymers

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10
Q

diploid cell

A

two sets of 23 (46 in total) ‘double’

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11
Q

haploid

A

one set of 23 chromosomes ‘half’

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12
Q

how does meiosis happen, full explanation

A

division 1
- replicate DNA (add an extra arm - become x shape)
- the chromosomes line up in the centre in pairs (one chromosome from one pairs with one chromosome from dad) in random order
- cell splits in two
division 2
- chromosomes line up in the centre again, the two arms are pulled apart and pulled to separate side of the cell
- cells divide in half again
produces FOUR HAPLOID genetically DIFFERENT cells
this is how gametes (egg and sperm cell) are produced

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13
Q

what does meiosis produce?

A

produces four haploid genetically unique cells

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14
Q

shape of DNA

A

a molecule of DNA contains two strands - the two strands twist around each other and are joined together by pairs of substances called bases (complementary base pairing) to form a double helix

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15
Q

structure of DNA

A

a strand of DNA is a polymer as it’s made of lots of monomers, each monomer is called a nucleotide

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16
Q

structure of a nucleotide

A

the base is attached to a sugar and each sugar is attached to a phosphate group

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17
Q

what are the four bases in DNA

A

adenine (A), thymine (T), cytosine (C), and guanine (G)

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18
Q

what are the complementary base pairs

A

A always pairs with T
G always pairs with C

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19
Q

nucleotide

A

grouping of a base, sugar and a phosphate

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20
Q

what two things form the backbone of the DNA strands

A

sugar and the phosphate group

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21
Q

what does cytosine pair with

A

guanine

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22
Q

what does adenine pair with

A

thymine

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23
Q

hydrogen bond

A

the weak bond between the base pairs

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24
Q

how many hydrogen bonds does cytosine and guanine form

A

3

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25
Q

how many hydrogen bonds does adenine and thymine form

A

2

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26
Q

what contains the coded instructions for a protein

A

the order of bases in a gene

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27
Q

how do the nucleotides in a strand connect

A

the phosphate of one nucleotide bonds with a sugar from an other nucleotide

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28
Q

what’s the complementary strand of the DNA sequence: ACTGAATG

A

T,G,A,C,T,T,A,C

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29
Q

genetic code

A

sequence of bases causing amino acids to be joined to create a certain protein

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30
Q

what is the method for extracting DNA

A

1) grind a piece of kiwi fruit with 10ml of salt solution
2) pour that into 100ml beaker and stir for 5 minutes with 5 drops of washing up liquid
3) filter the solution into test tubes
4) add 1 drop of protease solution
5) pipette, 3-5 ml of ice, cold ethanol, slowly down the side into the test tube
- leave the tube for a few minutes a layer forms between the filtrate and the ethanol - this is DNA

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31
Q

how does the sequence of bases create amino acids that create a specific protein

A
  • the bases are in blocks of 3 called triplets
  • the sequence of nucleotide bases devices the sequence of amino acids
  • all the amino acids (monomers) to create a protein (polymer)
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32
Q

what is transcription

A

the process of taking a single gene and making it into mRNA

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33
Q

what is translation

A

process of taking the mRNA strand and making it into a protien

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34
Q

what base gets replaced in mRNA

A

thymine gets replaced for uracil

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35
Q

process of transcription

A
  • enzyme called RNA polymerase binds to a region of non-coding DNA —> the enzyme DNA helicase unzips the two DNA strands
  • the enzyme then moves along one DNA strand and uses the coding DNA in the gene as a template to adds complementary RNA nucleotides
  • nucleotides link to form a strand of messenger RNA (mRNA)
  • once made the mRNA moves out the nucleus and attached to a ribosome
36
Q

process of translation

A
  • mRNA strand travels out the nucleus through small holes in its membrane called nuclear pores
  • in the cytoplasm, the mRNA strands attach to ribosomes
  • the ribosome moves along an mRNA strand 3 bases at a time (each triplet of bases is called a codon)
  • at each mRNA codon, a molecule of transfer RNA (tRNA) with complementary bases lines up.
  • each tRNA molecule is attached an amino acid
  • as the ribosome moves along, it joins up the amino acids from the RNA molecules together, forming a polypeptide
  • the polypeptide chain, and folds up to form a protein
37
Q

what are the stages in protein synthesis

A

transcription and then translation

38
Q

what’s a triplet of bases called?

A

a codon

39
Q

mutation

A

a change in the bases of a gene

40
Q

how can a mutation be caused

A

when DNA is not copied properly in cell division

41
Q

phenotype

A

what the organism looks like

42
Q

allele

A

different form of a gene

43
Q

what are the different types of mutations

A

normal allele - TAC GGT TCA GAT TTC CCT TAC
single substitution allele - TAC GGT TCT GAT TTC CCT TAC —> one base changed but nothing else
single deletion mutation - TAC GGT TCG ATT TCC CTT AC —> by getting rid of 1, everything moves up by 1
single addition mutation - TAC GGT TAC AGA TTT CCC TTA —> by adding 1, everything moves down by 1

44
Q

what happens when a mutation occurs in a non-coding DNA

A

RNA polymerase will not be able to bind and transcription will not occur

45
Q

genetic variation

A

difference in DNA (different alleles) among individuals gives us different characteristics

46
Q

homozygous

A

two identical versions of the same gene

47
Q

heterozygous

A

two different versions of the same gene

48
Q

gamete

A

a reproductive cell of an animal or plant

49
Q

dominant allele

A

produces a dominant phenotype in individuals who have one copy of the allele

50
Q

recessive allele

A

allele that when present with a dominant allele will not affect the individuals phenotype

51
Q

genotype

A

alleles in an organism

52
Q

how to present a dominant allele in a genetic diagram

A

capital letter

53
Q

how to present a recessive allele in a genetic diagram

A

lower case letter

54
Q

what sex chromosomes do females have

A

two X-sex chromosomes

55
Q

what sex chromosomes do males have

A

one X, one Y and a sperm contains either X OR Y

56
Q

how is gender determined

A

the 23rd pair of chromosomes in humans

57
Q

punnet square

A

a table that shows possible genotypes

58
Q

family pedigree chart

A

shows how genotypes types their resulting phenotypes are inherited in families

59
Q

what are the 4 blood types

A

A, B, AB, O

60
Q

codominance

A

when both alleles for a single gene affect the phenotype

61
Q

3 types of red blood cell antigens on the red blood cell membrane that determine your blood group (3 ‘maker molecules’)

A

A, B and O

62
Q

3 alleles that are responsible for the markers in the ABO system

A

IA IB IO

63
Q

what are the phenotypes and genotypes for A, B, AB, O blood types?

A

phenotype: A B AB O
genotypes: IA IA IB IB IA IB IO IO

64
Q

which of the following 3 alleles responsible for your type of blood is recessive to the others?

A

IO is recessive to both IA ans IB

65
Q

which blood type is a universal doner

A

blood type o because it doesn’t have A or B antigens so doesn’t get rejected by any immune systems and can be anywhere

66
Q

which blood type is a universal recipient

A

blood type AB because they can safely receive a blood transfusion of any other blood type as the other blood types either have the antigen A or B or for blood type O it doesn’t have any antigens to worry about

67
Q

sex-linked genetic disorder

A

disorderly that show a different pattern of inheritance in men and women

68
Q

which one of the human chromosomes is missing some genes

A

the human Y chromosome is much shorter than the human X chrormomes because it is missing some of the genes found on the X chromosome

69
Q

cystic fibrosis

A
  • genetic inherited disease
  • person with CF produces large quantities of mucus in the lungs and digestive system
    —> have problems with lungs and digestive system
70
Q

what type of allele is cystic fibrosis found on

A

recessive allele and this disease will only occur when the patient is homozygous (two recessive alleles)

71
Q

melanin

A

a protein that makes hair, eyes and skin darker in colour
e.g. a blue iris contains little melanin whereas a brown iris contains a lot of melanin

72
Q

mutation

A

a change in a gene that creates a new allele

73
Q

how does a mutation happen

A

when there is a mistake in copying DNA during cell division

74
Q

what is the Human Genome Project

A

the Human Genome Project started in 1990 and was completed in 2003; hundreds of scientists from all over the world collaborated together to determine the sequence of base pairs that made up the genome of a random man and woman

75
Q

how can mapping a persons genome help them

A
  • can indicate their risk of developing diseases that are caused by different alleles of genes
  • can help identify what medicines might be best to treat a persons illness
76
Q

polygenetic

A

when a phenotype is influenced by two or more genes
e.g. eye colour, height, skin colour

77
Q

how is genetic variation caused

A

by the different alleles inherited during sexual reproduction

78
Q

how is environmental variation caused

A

when the individual is affected by their surroundings
e.g. how well plant grows determines on how much light, water and nutrients it gets

79
Q

how is acquired characteristics caused

A

when a characteristic is a result of events that occur throughout their lifetime and will not be passed onto your offspring
e.g. tattoos, scars

80
Q

discontinuous data

A

where the data can only take a limited set of values

81
Q

continuous data

A

where the data can be any value at any range

82
Q

example of continuous data

A

height, weight, temperature, length

83
Q

example of discontinuous data

A

person’s blood group, the color of a species of bird

84
Q

possible mechanisms for variation in an organism:

A
  • genetic
  • environment
  • acquired characteristics
85
Q

why is protease added in the DNA extraction practical

A
  • protease breaks down proteins in the cell membrane
    AND
  • destroys enzymes that may break down the DNA
86
Q

why is ice cold ethanol added in the DNA extraction practical

A

to precipitate (see) the DNA because DNA is insoluable in ethanol

87
Q

Why do you have to grind fruit in DNA extraction?

A

breaks the cell, releasing the DNA

Biology GCSE (8 decks)

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