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B3 - Genetics Flashcards

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1
Q

How do animals reproduce?

A

Sexual reproduction

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2
Q

What process creates gametes?

A

Meiosis

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3
Q

What do we call the fusion of male and female gametes?

A

Fertilisation

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4
Q

Why will offspring always be genetically different to either one of their parents?

A

Because the offspring have a combination of the DNA of both of the parents

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5
Q

What type of cell are sperm and egg cells?

A

Haploid cells

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6
Q

What are haploid and diploid cells?

A

Haploid cells have half the amount of genetic material as a normal (diploid) cell (Haploids have 23 chromosomes and diploids have 460

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7
Q

What type of cell is formed at fertilisation?

A

A diploid is formed from the haploid cells that are the sperm and egg cells

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8
Q

What 2 gametes fuse together in plant sex?

A

Pollen and egg

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9
Q

How many parents are involved in asexual reproduction?

A

1

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10
Q

Are the offspring of asexual reproduction genetically unique?

A

No they are genetically identical

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11
Q

What process do fungi and plants use when they reproduce asexually?

A

Mitosis

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12
Q

How do bacteria reproduce?

A

Asexual reproduction

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13
Q

What process do bacteria use when they reproduce?

A

Binary fission

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14
Q

Which type of reproduction is quicker?

A

Asexual reproduction is quicker than sexual reproduction

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15
Q

Which type of reproduction leads to more genetic variation in the population?

A

Sexual reproduction leads to more genetic variation in the population

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16
Q

What are 2 downsides of asexual reproduction?

A

Low genetic variation means offspring are more susceptible to disease and the population would have a smaller chance of adapting to disease

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17
Q

Give 3 advantages of sexual reproduction

A

Because gametes fuse it leads to a large amount of variation, meaning the population is less likely to be wiped out by a disease or extreme event and they can adapt to changing conditions by evolution

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18
Q

Give 3 disadvantages of sexual reproduction

A

It requires 2 parents, individuals may have to spends lots of time and energy searching for a mate and may spend resources impressing them when it doesn’t aid survival

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19
Q

What is another name for a gamete?

A

A sex cell

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20
Q

Give 2 examples of gametes

A

Sperm cell and egg cell

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21
Q

In meiosis, how many times does the cell divide?

A

2

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22
Q

As a result of meiosis, how many cells are produced?

A

4

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23
Q

Are cells produced by meiosis genetically identical or unique?

A

They are genetically unique

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24
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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25
What is the structure of DNA and how many strands does it have?
DNA has a double helix structure and has 2 strands
26
Where is the DNA found in a human cell?
It is found in tight coils known as chromosomes
27
How many chromosomes are in a typical human cell?
23 pairs so 46 chromosomes
28
What are chromosomes in the 23rd pair known as?
Sex chromosomes
29
What chromosomes represent the female and male genders?
XX: Female XY: Male
30
What shape do chromosomes represent most of the time?
Most of the time they will represent half of an X - they only look like an X when they are duplicated ready for cell division
31
How can DNA code for proteins?
They can code for the sequence in which amino acids are joined together
32
What is a genome?
The entire set of genetic material in an organism
33
What do we call diseases that are caused by genes?
Inherited diseases
34
Where in the cell are chromosomes found?
In the nucleus
35
Why do our body cells contain 2 copies of each chromosome and what does this mean about specific genes?
Because one is from the mother and one from the father. It means that we have 2 copies of each gene; each different copy is a different allele
36
What does being homozygous or heterozygous for a certain gene mean?
If you are homozygous for a gene both alleles for the gene are the same; if you are heterozygous the alleles are different
37
What are the 2 types of allele?
Dominant or recessive
38
if you have a dominant and recessive allele, which will be expressed?
The dominant allele
39
How can a recessive allele be expressed?
if there are 2 of them
40
What is a genotype?
The 2 alleles present for a particular gene
41
What is a phenotype?
The characteristics an organism has as a result of their genotype
42
What are the monomers of DNA called?
Nucleotides
43
What are the 3 parts of a monomer?
The base, sugar and phosphate
44
What are the 4 types of bases in DNA?
Adenine, Thymine, cytosine and Guanine (A,T,C and G)
45
What are the pairings for the DNA bases?
Adenine to Thymine (AT) and Cytosine to Guanine (CG) and vice versa
46
What is a gene?
A small section of DNA, with a particular sequence of bases that codes for a protein
47
What is a set of 3 bases called?
A codon
48
What does each codon code for?
An amino acid
49
How does DNA relate to proteins?
The sequence of the bases in the DNA determines the sequence of amino acids in the chain. The chain of amino acids then folds to form a protein. Different sequences of amino acids lead to proteins with different shapes, allowing proteins to carry out different functions
50
What is a polypeptide?
A chain of amino acids
51
What is an enzyme?
A protein that is used to speed up the rate of chemical reactions
52
What do we call the proteins that carry messages around the body?
Hormones
53
What is transcription?
The copying of a single gene of DNA, to mRNA
54
Where does transcription take place?
The nucleus
55
Why does transcription have to happen?
The DNA itself is t4oo large to leave the nucleus
56
How is mRNA different to DNA?
mRNA is single stranded whereas DNA is double stranded and mRNA is shorter than DNA
57
Which organelle does the mRNA go to when it leaves the nucleus?
It passes through the cytoplasm to the ribosomes
58
What is translation?
The combination of amino acids to form a polypeptide
59
How many bases are needed to code for an amino acid?
3-it is a codon
60
What is the function of a ribosome?
To assemble proteins from amino acids
61
What base does uracil (U) replace in mRNA?
Thymine (T)
62
Who developed the laws of inheritance?
Gregor Mendel
63
What are alleles?
Alternative forms of the same gene
64
What did Mendel study?
The inheritance of different characteristics
65
What species did Mendel use in his experiments?
Pea plants
66
What 3 traits did Mendel study in his experiments
Colour of flowers, colour of peas and the height of the plant
67
How would you describe the genotype AA and why?
Homozygous dominant - both are the same allele, so is homozygous and both are uppercase so are dominant
68
How would you describe the genotype Hh?
Heterozygous - they are both different alleles
69
How would you describe the allele dd?
Homozygous recessive - they are both the same so are homozygous and are both lowercase so are recessive
70
Is cystic fibrosis a recessive or dominant condition?
It is recessive
71
What genotype would you need to have cystic fibrosis?
Homozygous recessive
72
What genotype would be a carrier for cystic fibrosis?
Heterozygous
73
What is a carrier?
Someone who only carries one copy of a recessive allele and so doesn't suffer from the condition
74
What 2 factors contribute to variation in a population?
An individual's characteristics are determined by both the genes they inherit and the environment they are exposed to . This means that both contribute to the variation between organisms. Often the genes and environment will interact to create further variation
75
What is a mutation?
A change in the DNA code
76
What factors are involved in determining body mass?
Genetic and environmental factors
77
What is continuous variation?
Differences in a characteristic within the species that change gradually over a range of values, such as height or body mass. These characteristics are usually influenced by multiple genes
78
What does polygenic mean?
Characteristics or conditions influenced by multiple genes, rather than a single gene
79
What is discontinuous variation?
Differences between individuals within a species where the characteristic has distinct forms without overlap
80
Name 2 characteristics that show continuous variation
Hair colour and strength
81
What does survival of the fittest mean?
The individuals with the most favourable characteristics are most likely to survive
82
What is evolution?
The process by which the inherited characteristics of a species change over time due to natural selection. In some cases this may result in the formation of a new species
83
Name 2 things that provide evidence for evolution
Fossil records and the spread ofantibiotic resistance
84
Describe a series of events that might result in zebras being fast runners
Must include: A mutation arises that allows some zebras to run faster / there is variation among the zebra population so that some are faster The faster zebras are more likely to survive and pass on their fast alleles. This repeats over multiple generations Until the species has evolved to run faster because the fast allele is spread through the population
85
Name 2 things that can increase the risk of mutations
Ionising radiation and carcinogens like those in cigarette smoke
86
Where do most mutations occur?
non-coding DNA
87
What does it mean for a gene to be expressed?
It's turned on, so the proteins it codes for will be produced
88
What happens in a substitution reaction?
One base in the sequence is replaced with a different base
89
Describe how a change in a base in the gene for an enzyme could affect how it functions
A change in the base will change the codon which changes the amino acid it codes for, so there will be a different sequence of amino acids so the polypeptide will fold into a differently shaped enzyme. The enzyme may have a differently shaped active site, meaning it may no longer be complementary to the substrate, which would mean it couldn't form and enzyme-substrate reaction so wouldn't catalyse as well
90
What was the Human Genome Project?
A project in which scientist set out to map the human genome, identifying 20,500 new genes and 2,000 genes linked to diseases
91
Why is understanding the Human Genome important?
It helps us understand how genetic diseases work so we can take preventative steps and detect risks early. It also allows specific drugs and medicines to be tailored to a patients specific genetic makeup
92
What are 3 drawback of genetic screening?
It can cause stress and mental health risks, it can cause unfair treatment in jobs and insurance and there are concerns about the mis-use of genetic data

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