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BIOLOGY > Genetics - Topic 3 > Flashcards

Genetics - Topic 3 Flashcards

1
Q

what does diploid mean

A

it has 2 copies of each chromosome

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2
Q

what are gametes

A

sex cells such as testes and egg cells

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3
Q

are gametes haploid or diploid

A

gametes are haploid - they contain half the number of chromosomes in a normal cell

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4
Q

what is a zygote

A

a fertilised egg which is produced when a male gamete fuses with a female gamete

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5
Q

how many chromosomes does a zygote have

A

the full number of chromosomes

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6
Q

how is meiosis different to mitosis

A

it doesn’t produce identical cells
It produces cells which have half the normal number of chromosomes

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7
Q

explain the process of meiosis

A
  1. The cells duplicates its genetic information, forming 2 armed chromosomes and after replication the chromosomes arrange themselves into pairs
  2. In the first division, the chromosome pairs line up in the centre of the cell
  3. the pairs are then pulled apart so each new cell only has one copy of each chromosome.
  4. Some of the father’s chromosomes and some of the mothers chromosomes. This mixing is important as it mixes their genes creating genetic variation in the offspring
  5. In the second division, chromosomes line up in the centre of the cell and the arms of the chromosomes are pulled apart
  6. You get 4 haploid daughter cells which are genetically different from the others
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8
Q

what is asexual reproduction

A

reproduction which only involves one parent and happens by mitosis

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9
Q

what are the advantages of asexual reproduction

A

it is faster than sexual reproduction as it only needs one parent
uses less energy
no chance of genetic disease being passed to offspring
2 parents are not required

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10
Q

what are the disadvantages of asexual reproduction

A

the all look the same
no genetic variation

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11
Q

what are the advantages of sexual reproduction

A

it has genetic variation in offspring
variation increases chance of survival when there is a change in the environment
adaptation is possible
each organism is unique

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12
Q

what are the disadvantages of sexual reproduction

A

diseases can be passed on
it is very slow
uses more energy
2 mates are required
not everyone can have a child

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13
Q

what are chromosomes

A

coiled strands of really long DNA

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14
Q

what does DNA stand for

A

deoxyribonucleic acid

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15
Q

what is DNA

A

a polymer made up of two strands coiled to form a double helix

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16
Q

what is a gene

A

a section of a DNA molecule that codes for a specific protein

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17
Q

what is a genome

A

the entire DNA of an organism

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18
Q

What is DNA made up of

A

nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar. It is also strands linked by a series of complementary base pairs joined by weak hydrogen bonds

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19
Q

what are the complementary bases in DNA

A

Adenine and Thymine

Cytosine and Guanine

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20
Q

how many hydrogen bonds are between A and T

A

2

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21
Q

how many hydrogen bonds are between C and G

A

3

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22
Q

Describe the structure of DNA (4)

A

DNA has a double helix structure. Adenine and Thymine are complementary bases and Guanine and Cytosine are as well. A and T is held together by 2 hydrogen bonds and C and G is held together by 3 hydrogen bonds. Each base is connected to a sugar and each sugar is attached to a phosphate group. This makes up the backbone of the DNA.

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23
Q

How do you extract DNA from fruit

A
  1. Mash some strawberries with a pestle and mortar and then put them in a beaker containing a solution of detergent and salt. Mix well.
  2. Filter the mixture to get the froth and big, insoluble bits of cell out
  3. Gently add some ice-cold alcohol e.g. ethanol to the filtered mixture
  4. The DNA will start to come out of the solution as it is not soluble in cold alcohol. It will appear as a string white precipitate that can be carefully fished out with a glass rod
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24
Q

why is detergent added to the strawberries when extracting DNA

A

The detergent will break down the cell membranes to release the DNA

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25
Q

why is salt added to the strawberries when extracting DNA

A

salt makes DNA stick together

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26
Q

what are proteins made up of

A

chains of amino acids

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27
Q

why do proteins have different functions

A

amino scid chains fold up to give each protein a different, specific shape

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28
Q

what decides the order of amino acids in a protein

A

the order of genes

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29
Q

what decides the order of amino acids in a protein

A

the order of genes

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30
Q

how does the order of genes determine the order of amino acids in a protein

A

each amino acid is coded for by a sequence of three bases in the gene - this is called a base triplet.

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31
Q

what are non coding parts of DNA

A

regions of DNA which don’t code for any amino acids

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32
Q

what is a mutation

A

a rare, random change to an organisms DNA base sequence that can be inherited.

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33
Q

how are genetic variants produced

A

if a mutation happens in a gene

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34
Q

what does a change in the amino acid sequence do

A

change the shape of the final protein and so its activity also changes. The activity of an enzyme might increase, decrease or stop altogether and could and up changing the characteristic / phenotype of an organism

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35
Q

what is the first stage of protein synthesis called

A

transcription

36
Q

what is the second stage of protein synthesis called

A

translation

37
Q

where does transcription takes place

A

in the cell nucleus

38
Q

where does translation take place

A

in the cell cytoplasm and involves ribosomes which join amino acids together to make a protein

39
Q

where is DNA stored

A

in the cell nucleus

40
Q

why can’t DNA move out of the nucleus

A

it is really big

41
Q

what is mRNA

A

mRNA (messenger RNA) is a molecule that carries genetic information from DNA to the ribosome for protein synthesis.

42
Q

what is the difference between mRNA and DNA

A

mRNA is shorter and only a single strand and uses uracil instead of thymine as a base

43
Q

what does RNA polymerase do

A

it joins together RNA nucleotides to make the mRNA

44
Q

what does RNA polymerase do

A

it joins together RNA nucleotides to make the mRNA

45
Q

what happens in Transcription

A
  1. RNA polymerase binds to a region of non-coding DNA in front of a gene.
  2. The 2 DNA stands unzip and the RNA polymerase moves along one the strands of DNA. It uses the coding DNA in the gene as a template to make the mRNA.
  3. Once made, the mRNA molecule moves out of the nucleus and joins with a ribosome in the cytoplasm
46
Q

what happens in Translation

A

(the process is) translation (1)
(mRNA ) leaves the nucleus and enters the cytoplasm (1)
(mRNA joins to) ribosomes(1)
tRNA carries amino acids (1)
tRNA joins to mRNA / bases on tRNA matches bases on mRNA (1)
(bases read as) {sets of three/ triplets / idea of codons} (1)
(ribosome / mRNA holds tRNA so) amino acids are joined together / to make polypeptides (1)

47
Q

how do genetic variants in the non-coding DNA of a gene affect phenotype

A

if a mutation happens in the non coding region of DNA then it could affect the ability of RNA polymerase to bind to it

and how well RNA polymerase can bind to this region of DNA will affect how much mRNA is transcribed

therefore how much protein is produced

and depending on the function of the protein the phenotype of the organism may be affected by how much of it is made.

48
Q

what are most phenotypic features a result of

A

multiple genes rather than single gene inheritance

49
Q

why are there differences in inherited characteristics

A

this is because different alleles code for different forms of the same protein

50
Q

what is an allele

A

The different forms of the gene that determines a certain characteristic

51
Q

what is a dominant allele

A

Only one (out of the two alleles) is needed for it to be expressed and for the corresponding phenotype to be observed.

52
Q

what is a recessive allele

A

Two copies are needed for it to be expressed and for the corresponding the phenotype to be observed.

53
Q

what is homozygous

A

When both inherited alleles are the same (i.e. two dominant alleles or
two recessive alleles).

54
Q

what is heterozygous

A

When one of the inherited alleles is dominant and the other is
recessive

55
Q

what is a genotype

A

the combination of alleles you have such as CC or cC

56
Q

what is a phenotype

A

your characteristics e.g. blonde hair or blue eyes

57
Q

what did Mendel do

A

he crossed two pea plants, one which was tall and one which was a dwarf and the offspring were all tall. He then bred two tall pea plants together and he got 3 tall plants and 1 dwarf plant

58
Q

what did Mendel’s experiments show

A

he had shown that the height characteristics in pea plants was determined by separately inherited ‘hereditary units’ passed on from each parent.

59
Q

what conclusions did Mendel get about hereditary in plants

A
  1. Characteristics in plants are determined by “hereditary units”
  2. Hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
  3. Hereditary units can be dominant or recessive
60
Q

what was the importance of Mendel’s work

A

it allowed us to understand the mechanism of inheritance

61
Q

how many pairs of chromosomes are in the human body

A

23 pairs

62
Q

what pair of chromosome determines the sex of the offpspring

A

the 23rd pair as the first 22 pairs are identical

63
Q

how does the 23rd pair of chromosome determine the sex of the offspring

A

egg cells only have one X chromosome so if the final pair is XX the offspring is a girl

sperm cells can have either X or Y chromosome so if the final pair is XY, it is a boy

64
Q

how are sex linked genetic disorders inherited

A

if the faulty alleles are located on sex chromosomes

65
Q

what is codominance

A

when two alleles of a gene are expressed in the same phenotype

66
Q

what are the four potential human blood types

A

A, B, O, AB

67
Q

what are the alleles for group A blood

A

A and O alleles

A and A alleles

68
Q

what are the alleles for group B blood

A

B and B alleles

B and O allleles

69
Q

what are the alleles for group AB blood

A

A and B

70
Q

what are the alleles for group O blood

A

O and O

71
Q

what is genetic variation

A

different characteristics as a result of mutation and sexual reproduction

72
Q

what is environmental variation

A

different characteristics caused by an organisms environment

73
Q

how does genetic variation influence phenotype

A

there are new alleles rising through mutations and sexual reproduction also causes genetic variation as it results in alleles being combined in a lot of different ways

74
Q

how does environmental variation influence phenotype

A

the environment an organism lives and grows in causes differences between members of the same species

75
Q

what are some examples of genetically determined characteristics

A

flower colour in violets
eye colour
blood group
inherited disorders

76
Q

what are some examples of genetically and environmentally determined characteristics

A

height
intelligence
health

77
Q

how does extensive genetic variation arise in a population

A

through mutations

78
Q

what are the effects of genetic mutations on phenotype

A

most genetic mutations have no effect on the phenotype, some mutations have a small effect on the phenotype and rarely a single mutation will significantly affect the phenotype

79
Q

what was the outcome of the human genome project

A

to find every single human gene

80
Q

what are the potential applications of the human genome project within medicine

A

prediction and prevention of disease
testing and treatment for inherited disease
new and better medicines

81
Q

how does the human genome project help predict and prevent disease

A

if doctors knew what alleles predisposed people to what diseases, we can all get individually tailored advice on the best diet and lifestyle to avoid out likely problems

82
Q

how does the human genome project help test and treat for inherited disorders

A

scientists can now identify the genes and alleles that are suspected of causing an inherited disease more quickly so once the allele is identified, people can be tested for it and it may be possible to develop better treatments

83
Q

how does the human genome project help develop new and better medicines

A

we can design new drugs that are specifically tailored to people with that allele and determine what dosage is most appropriate for particular drugs in different patients.

84
Q

what are the ethical issues raised by genetic analysis

A

if a person knows they have alleles which make them more susceptible for a certain disease, it makes them more stressed

someone who knows they have a faulty allele may be under pressure not to have children to pass it on to

leads to discrimination, difficulty getting employment, getting life insurance

85
Q

Describe how a section of DNA determines the structure of a protein.
(4)

A

ref to a gene (coding for protein) (1)
* sequence of bases determines sequence of amino acids (1)
* idea of one code / triplet /codon / 3 bases (for one amino acid) (1)
* several amino acids make up a protein / (poly)peptide (1)

86
Q

Explain how the Human Genome Project has contributed to advances in
medicine.

A

genes / base sequence (on human chromosome) identified (1)
identification of faulty / mutated genes (1)
people can be tested for a genetic disorder (1)
idea that appropriate personalised medication can be given

87
Q

Describe what effect a mutation could have on the action of an enzyme. (3)

A

a mutation is a change in a gene (sequence) (1)
* (change in DNA) causes a change in order of amino acids (1)
* change in shape of {active site / protein / enzyme} (1)
* prevent / reduce binding to substrate (1)
* enzyme can no longer function / reduced function (1)
* enzyme could be more effective (1)

BIOLOGY (9 decks)

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