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A LEVEL BIOLOGY > 9 - Inheritance (C2) > Flashcards

9 - Inheritance (C2) Flashcards

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1
Q

What is the definition of a gene?

A

A sequence of DNA that codes for a polypeptide and which occupies a specific locus on a chromosome

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2
Q

What is the definition of an allele?

A

A variant nucleotide sequence for a particular gene at a given locus, which codes for an altered phenotype

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3
Q

What does homozygous mean?

A

The alleles of a particular gene are the same

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4
Q

What does heterozygous mean?

A

The alleles of a particular gene are different

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5
Q

What is the genotype of an individual?

A

The alleles that they contain

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6
Q

What is the phenotype of an individual?

A

A description of their appearance, including characteristics that can’t be seen, e.g. their blood group

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7
Q

What is a dominant allele?

A

An allele that has the same effect on the phenotype of a heterozygote as a homozygote

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8
Q

What is a recessive allele?

A

An allele is only expressed when in a homozygous pair and when no dominant allele is present

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9
Q

What is co-dominance?

A

When both alleles contribute to the phenotype

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10
Q

What is monohybrid inheritance?

A

The inheritance of a single gene

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11
Q

Why are peas useful to be used in inheritance experiments?

A
  • They’re easy to grow
  • Their flowers can self-fertilise and cross-fertilise
  • They make flowers and fruit in the same year
  • They make a large number of seeds from each cross
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12
Q

Why did Mendel chose to study pairs of contrasting characteristics e.g. tall or dwarf plants?

A
  • They’re controlled by single genes
  • They’re controlled by genes on different chromosomes
  • Easy to tell apart
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13
Q

What is continuous variation?

A

Variation with a range of values that’s controlled by a number of genes e.g. height

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14
Q

What is incomplete dominance?

A

When neither allele is dominant so the offspring phenotype is intermediate between that of the 2 homozygotes e.g. red flower + white flower -> pink flower

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15
Q

What are linked genes?

A

Genes that are on the same chromosome and therefore are not separated at meiosis

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16
Q

What increases the likelihood of crossing over of genes?

A

The further apart 2 genes are on a chromosome, the more opportunity there is for crossover to occur between them

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17
Q

What number is the degrees of freedom?

A

1 less than the number of classes of data

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18
Q

Why are the sex chromosomes called heterosomes?

A

Because they’re different sizes

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19
Q

What are the autosomes?

A

The 22 pairs of identical genes in humans (non-sex chromosomes)

20
Q

What is a sex-linked gene?

A

A gene on the X chromosome that gives rise to a sex-linked condition

21
Q

What are 2 features of mutations?

A
  • Spontaneous

- Random

22
Q

What is a mutation?

A

The change of the structure of a gene resulting in a variant form

23
Q

What mutations are inherited?

A

Only those that occur in gametes

24
Q

What can mutation rates be increased by?

A
  • Ionising radiation

- Mutagenic chemicals e.g. those in cigarette smoke

25
Q

What can cause gene or point mutation?

A

DNA not being copied accurately in S phase

26
Q

What can cause chromosome mutation?

A

When chromosomes get damaged and they repair themselves incorrectly, altering their structure and affecting lots of genes

27
Q

What is aneuploidy and what causes it?

A
  • Chromosome being lost or added
  • When chromosomes fail to separate to poles of dividing cells
  • Or when chromosomes fail to separate at anaphase 2
28
Q

What is polyploidy and what causes it?

A

Number of chromosomes doubling if the cell fails to divide following the first nuclear division after fertilisation

29
Q

Why are bacteria often used in mutation experiments?

A

They have:

  • Short life cycle
  • High rate of mutation
30
Q

What is non-disjunction?

A

When a faulty cell division in meiosis causes 1 of the daughter cells to receive 2 copies of the chromosome whilst the other receives none

31
Q

What are hermaphrodite organisms?

A

Those that produce both male and female gametes

32
Q

What is a carcinogen?

A

An agent that causes cancer

33
Q

What are tumour suppressor genes?

A

Genes that regulate mitosis and prevent cells dividing too quickly

34
Q

What is an oncogene?

A

A proto-oncogene with a mutation that results in cancer

35
Q

How can proto-oncogenes cause cancer?

A

Mutations can cause them to be switched on permanently causing rapid, repeated mitosis

36
Q

What is epigenetics?

A

The control of gene expression by modifying DNA or histones, but not by affecting the DNA nucleotide sequence

37
Q

What is the epigenetic modification of DNA methylation?

A
  • Cytosine can have a methyl or hydroxymethyl group added

- Areas of DNA that are heavily methylated are less likely to be transcribed

38
Q

What is the epigenetic histone modification following translation?

A
  • e.g. attaching an acetyl group to the amino acid lysine
  • These changes to histone proteins alter their interaction with DNA and changes the arrangement of the nucleosomes
  • Coiling is more relaxed and transcription factors and RNA polymerase have access to the DNA, so transcription is increased
39
Q

What is genomic imprinting?

A

If genes are activated into gametes, the inactivation may be transferred to the next generation

40
Q

When do you accept the null hypothesis in a chi squared test?

A
  • If chi squared value < critical value
  • This means there’s no sig diff between observed and expected
  • Accept null
41
Q

What is complete/total linkage?

A
  • When 2 genes have their loci close together on the same chromosome so tend to occur in gametes in parental combinations
  • Causes 3:0:0:1
42
Q

What is the locus?

A

The position of a gene on a chromosome

43
Q

What is a benign tumour?

A

One that is not growing in size

44
Q

What is a malignant tumour?

A

A cancerous one

45
Q

What is a monohybrid cross?

A

A cross in which only one gene is being considered e.g. TT x tt

46
Q

What is a dihybrid cross?

A

A cross in which 2 genes are considered e.g. TTRR x ttrr

A LEVEL BIOLOGY (13 decks)

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