biology gcse > Genetics, Inheritance And Evolution > Flashcards

Genetics, Inheritance And Evolution Flashcards

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1
Q

Genome

A

The entire DNA of organism

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2
Q

Chromosome

A

Made of DNA and protein. Found in the nucleus of eukaryotic cells. Contains genes.

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3
Q

Gene

A

A section of DNA that codes for a specific protein

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4
Q

Karyotype

A

A photograph of an individuals chromosomes, taken when a cell is about to divide

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5
Q

Allele

A

Different forms of a gene, that give differences in inherited characteristics

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6
Q

Diploid

A

Contains two sets of chromosomes, in body cells

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7
Q

Haploid

A

Contains only one set of chromosomes, these are the gametes

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8
Q

Gamete

A

Male and female sex cells made in meiosis

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9
Q

Zygote

A

A fertilised egg cell

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10
Q

Boy chromosomes

A

XY

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11
Q

Girl chromosomes

A

XX

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12
Q

How many chromosomes do humans have?

A

46 (23 pairs)

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13
Q

Sex cells are

A

Haploids as they contained only one copy of each chromosome

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14
Q

Monomers that make up DNA

A

Nucleotides

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15
Q

DNA structure

A

Two strands coiled to form a double helix, linked by a series of paired bases

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16
Q

Four bases

A

Adenine, cytosine, guanine, thymine

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17
Q

Sequence of three bases

A

Triplet/codon, which codes for one amino acid

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18
Q

Sequence of amino acids in a protein determine

A

The shape of a protein

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19
Q

Protein shape determines

A

Protein function

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20
Q

DNA compared to RNA

A

Double stranded, Thymine instead of Uracil, longer

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21
Q

RNA compared to DNA

A

Single stranded, Uracil instead of Thymine, shorter

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22
Q

tRNA shape

A

Clover shape

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23
Q

Where does transcription happen?

A

Nucleus

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24
Q

Transcription conversion

A

DNA to mRNA

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25
Translation conversion
mRNA to protein
26
Where does translation occur?
Ribosomes in the cytoplasm
27
Transcription
-hydrogen bonds between the two DNA strands are broken (one strand is the template strand) -RNA nucleotides form hydrogen bonds with complementary DNA bases -RNA polymerase joins up the nucleotides to make a molecule of mRNA -mRNA travels to the cytoplasm and binds to a ribosome
28
Translation
- tRNA with a complementary anticodon binds to the first codon on the mRNA - brings a specific amino acid with it - a peptide bond forms between the amino acids - the tRNA leaves the ribosome - ribosome moves to the next codon, forms a chain of amino acids (protein)
29
Nucleus of a cell contains
Chromosomes on which genes are located
30
When does mitosis occur
During growth, repair, cloning and asexual reproduction
31
Mitosis
Cell division that Produces genetically identical cells
32
Asexual reproduction results in
- rapid increase in numbers - all offspring genetically identical But if the environment changes they are all susceptible to change
33
Diploid number of chromosomes in human cells
46
34
Haploid number of cells in humans
23
35
Mitosis stages
- chromosomes shorten and thicken - they replicate themselves so there are 2 copies of each - they are pulled to each side of the cells - they line up along the middle of the cell - cell divides down the middle - 2 genetically identical cells are created
36
Meiosis produces
- gametes - 4 haploid cells, each with half the number of chromosomes - which are genetically different - from 2 divisions
37
What produces genetic variation of offspring
Random fertilisation, as it is random which egg is released during ovulation and which sperm fertilises it.
38
Monohybrid
Inheritance involving a single gene
39
Genotype
Alleles an organism has for a certain characteristic
40
Phenotype
How a gene is expressed
41
Homozygous
Genotype with the same alleles of a gene
42
Heterozygous
Genotype with different alleles of a gene
43
Dominant
Allele of a gene that is expressed in a heterozygote
44
Recessive
Allele that isn’t expressed in the phenotype when a dominant allele of the gene is present
45
Diploid
Number of chromosomes found in body cells, containing both chromosomes of each homologous pair
46
Haploid
Number of chromosomes found in gametes, containing one chromosome from each homologous pair
47
When are alleles codominant
If two alleles are expressed in the same phenotype, eg red and white flowers can produce pink
48
Polygenic
Controlled by many genes, usually shows continuous variation. They are greatly influenced by environmental factors. eg. Height, body mass
49
Polygenic characteristics have phenotypes that can
Show a wide range of combinations in features. The inheritance of those is polygenic inheritance eg. Eye colour.
50
Mutation is
Rare and random change to the DNA base sequence that can be inherited
51
What does mutation do
- provides new alleles - source of variation - a change in the DNA nucleotide of an allele - may not immediately affect the phenotype - can be beneficial, neutral or harmful
52
Causes of mutation
- ionising radiation, eg. UV, x rays - chemical mutagens eg. Tar from cigarette smoke
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How does mutation affect protein synthesis
- the base sequence of the complementary mRNA is changed - a modified mRNA will be translated and will code for different sequences of amino acids - the shape of the protein is altered
54
Harmful effects of mutations
- alter the base pair sequence of amino acids in DNA, so it codes for a different protein which may destroy the protein’s normal function - may cause genetic disorders or an obvious effect on the phenotype
55
Harmful mutations
- substitution (only one codon is changed) - insertion (causes a frame shift, all codons after the extra base are changed) - deletion (causes a frame shift)
56
Codon
Three bases
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Neutral mutations
- most mutations have no effect on the phenotype - The DNA base change might code for the same amino acid, with no effect on the protein’s normal function - may not affect chances of survival
58
Different types of variation in a species
Inherited/genetic (eg. Eye colour) , environmental (eg. Scar) , or both (eg. Body mass)
59
Beneficial mutations
Allows organisms to be better adapted to the environment, increasing chances of survival
60
Species
Group of organisms that can breed together and produce fertile offspring
61
Explain evolution
- there is natural variation in all species - a chance mutation produces a new allele - this gives the organism a selective advantage (useful for changing environment) - those better suited will survive and reproduce - beneficial allele will be passed on, and will increase in frequency in a population - overtime (millions of years) the species will evolve
62
General mutations effect
- most have no effect on the phenotype - some have a small effect - very rarely it will have a significant effect
63
Antibiotic-resistant bacteria
- antibiotic resistance can increase in populations due to mutations, giving the bacteria a selective advantage - individual bacteria are more likely to survive, reproduce, and pass on the beneficial allele (natural selection)
64
Superbug
Bacteria that is resistant to most known antibiotics
65
Protein synthesis stages
- transcription occurs in nucleus: • production of mRNA from DNA - translation occurs on ribosome, and mRNA binds to it • tRNA brings amino acids • codon are complementary and bind to anticodon • amino acids join together and polypeptide produced
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