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Biology GCSE > DNA and the Genome, Genetic Inheritance, Variation and Evolution > Flashcards

DNA and the Genome, Genetic Inheritance, Variation and Evolution Flashcards

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1
Q

What is the genetic material in the nucleus composed of?

A
  • DNA
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2
Q

What is DNA?

A

a long polymer made of 2 strands twisted into a double helix

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3
Q

What are chromosomes?

A
  • long lengths of DNA tightly coiled
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4
Q

What are genes?

A
  • short sections of DNA
  • codes for specific sequence of amino acids
  • forms proteins
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5
Q

What can scientists do now that they have sequenced the entire human genome?

A
  • search for genes linked to particular diseases
  • understanding and treating inherited disorders
  • tracing of past human migration patterns
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6
Q

What is a double helix made out of?

A
  • repeating nucleotides joined together = 2 long strands
  • bases attached to each sugar at 90 degrees
  • meets in the middle, holds 2 strands together
  • 2 strands twisting around each other = double helix
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7
Q

What are nucleotides made of?

A
  • a sugar
  • a phosphate group
  • a base
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8
Q

What codes for a particular amino acid in a protein?

A
  • 3 bases
  • order of every set of 3 bases = a type of amino acid in protein
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9
Q

Where are the instructions to build all of the proteins required in the cell?

A

DNA in the nucelus

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10
Q

Describe protein synthesis

A

1) single strand copy of DNA- mRNA made in nucleus
2) moves from nucleus to ribosome
3) carrier molecules bring specific amino acids in right order based on mRNA template
4) forms chain of amino acids (3 bases = 1 amino acid)
5) chain complete = folds into unique shape
6) unique shape = enables protein to do job (enzyme, hormones, forming structures- collagen)

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11
Q

Do all parts of DNA code for proteins?

A
  • No
  • non-coding parts can switch genes on and off
  • variations = changes in how genes are expressed
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12
Q

How do mutations in coding DNA affect protein synthesis?

A
  • causes shape of protein to be different
  • most do not alter function/ appearance (slight alteration)
  • few mutations = altered protein, different shape
  • enzyme may no longer fit substrate binding site/ structural protein loses its strength
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13
Q

What is a gamete?

A

a sex cell formed by meiosis

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14
Q

What is an allele?

A

a variation of a gene

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15
Q

What is a dominant allele?

A

an allele that only needs one copy to be expressed

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16
Q

What is a recessive allele?

A

an allele that needs two copies to be expressed

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17
Q

What is homozygous?

A

having two copies of the same allele for a trait

18
Q

What is heterozygous?

A

having two different alleles for a trait

19
Q

What is a genotype?

A

the combination of alleles that an organism has

20
Q

What is phenotype?

A

The expressed genotype of an organism

21
Q

What is polydactyly caused by?

A

a dominant allele

22
Q

What is cystic fibrosis caused by?

A

a recessive allele

23
Q

How many pairs of chomosomes does a human have?

A

23 pairs

24
Q

What does embryo screening do?

A

detects genetic disorders in embryos

25
Q

Describe natural selection

A
  • mutations occur in populations (common)
  • mutations occasionally alters phenotype
  • might be more suited to changing conditions
  • individual more likely to survive and reproduce
  • passes mutation to offspring
26
Q

What is evolution?

A
  • change in inherited characteristics of a population over time
  • through natural selection
  • may result in formation of new species
27
Q

Why does genetic variation occur?

A

differences of alleles inherited by individuals

28
Q

Why does environmental variation occur?

A

if individuals develop in different conditions

29
Q

Why is there a variation in the population?

A

mixture of environmental and genetic variation

30
Q

What does the theory of evolution by natural selection state?

A
  • all species of living things have evolved from simple life forms that first developed three billion years ago
31
Q

At what point do two populations of the same species become two different species?

A
  • phenotypes so different that they could no logner interbreed to produce fertile offspring
32
Q

How long have humans been selectively breeding plants and animals?

A
  • thousands of years
  • bred food crops from wild plants
  • domesticated animals
33
Q

Describe selective breeding

A
  • choose parents with desired characteristic from population
  • bred together
  • choose offspring with desired characteristic and breed together
  • continues over many generations until all offspring show desired characteristic
34
Q

How are males chosen for certain characteristics that only females have?

eg milk

A

choose from male’s female offspring

35
Q

What can inbreeding lead to?

A
  • some breeds being particularly prone to disease or inherited defects
36
Q

What are plants selectively bred for?

A
  • food crops with disease resistance
  • large or unusual flowers
37
Q

What are animals selectively bred for?

A
  • produce more meat and milk
  • domestic dogs with gentle nature
38
Q

What are crops genetically modified for?

A
  • add resistance to pests
  • increase crop yield
  • resistant to herbicides (only kills weeds, not crops)
39
Q

How was genetic engineering used for production of human insulin?

A
  • gene for human insulin “cut out” from chromosomes of human cells
  • added to genome of bacterial cells
  • bacteria makes insulin
  • done at large industrial scale, collected
  • increases supply of human insulin for people with diabetes
40
Q

How does genetic engineering work?

A
  • enzymes used to “cut out” or isolate required gene
  • required gene inserted into vector (viruses/ bacterial plasmids)
  • vector inserts gene into cells of target organism
41
Q

What are the concerns of genetic engineering?

A
  • reduces biodiversity, populations of wild flowers/ insects decreases around GM crops
  • unknown long term effects of eating GM crops for humans
42
Q

What could gene therapy treat?

what are the concerns?

A
  • genetic disorders eg cystic fibrosis

ethical objections to altering human genome

Biology GCSE (9 decks)

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