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Biology A-level > Chapter 16: Inherited Change > Flashcards

Chapter 16: Inherited Change Flashcards

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1
Q

How many PAIRS of matching chromosomes do humans have?

A

22

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2
Q

what is the definition of ‘homologous’?

A

similar in structure and composition

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3
Q

what are the non-matching chromosomes in humans?

A

the sex chromosomes

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4
Q

name the two types of chromosomes

A

sex chromosomes

autosomes (all the other chromosomes)

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5
Q

each chromosome has a characteristic set of … which code for different features

A

genes

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6
Q

what is the locus?

A

the position on the chromosome where genes for particular characteristics are always found

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7
Q

definition of a homologous chromosome

A

pair of chromosomes in a diploid cell that have the same structure as each other, with the same genes at the same loci, and that pair together to form a bivalent during the first division of meiosis

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8
Q

definition of a gene

A

a length of DNA that codes for a particular protein or polypeptide

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9
Q

definition of an allele

A

a particular variety of a gene

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10
Q

definition of a locus

A

the position at which a particular gene is found on a particular chromosome; the same gene is always found a the same locus

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11
Q

name the two types of nuclear division

A

growth and sexual reproduction

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12
Q

what type of nuclear division is growth?

A

mitosis

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13
Q

what type of division is sexual reproduction?

A

meiosis

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14
Q

define ‘haploid’

A

a cell which contains only one complete set of chromosomes

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15
Q

events in middle prophase 1

A
  • homologous chromosomes pair up (synapsis)
  • each pair is a bivalent
  • centrosomes move to opposite ends of the nucleus
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16
Q

events in metaphase 1

A

-bivalents line up across equator of spindle, attatched by centromeres

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17
Q

events in late prophase 1

A
  • nuclear envelope breaks up as in mitosis
  • crossing over of chromatids may occur
  • nucleolus ‘disappears’
  • spindle forms
18
Q

events in metaphase 1

A

-bivalents line up across equator of the spindle, attached by centromeres

19
Q

events in anaphase 1

A
  • centromeres do not divide

- whole chromosomes move towards opposite ends of the spindle, centromeres first, pulled by microtubules

20
Q

events in telophase 1

A

-nuclear envelope re-forms
-nucleolus re-forns
cytokinesis
-chromosomes reach poles of spindle

21
Q

events in prophase 2

A
  • nuclear envelope and nucleolus disperse

- centrosomes and centrioles replicate and move to opposite poles of the cell

22
Q

events in metaphase 2

A

chromosomes line up separately across equator of spindle

23
Q

events in anaphase 2

A
  • centromeres divide

- spindle microtubules pull the chromatids to opposite poles

24
Q

events in telophase 2

A

four haploid daughter cells are formed

25
Q

define ‘spermatogenesis’

A

the formation of male gametes

26
Q

define ‘oogenesis’

A

the formation of female gametes

27
Q

define ‘genotype’

A

the alleles possessed by an organism

28
Q

define ‘homozygous’

A

having two identical alleles of a gene

29
Q

define ‘heterozygous’

A

having two different alleles of a gene

30
Q

what is an ‘allele?’

A

different varieties of the same gene

31
Q

define ‘phenotype’

A

its characteristics, often resulting from an interaction between its genotype and its environment

32
Q

define ‘dominant allele’

A

one whose effect on the phenotype of a heterozygote is identical to its effect in a homozygote

33
Q

define ‘recessive allele’

A

one that is only expressed when no dominant allele is present

34
Q

define ‘codominant alleles’

A

where both alleles have an effect on the phenotype of a heterozygous organism

35
Q

define ‘F1 generation’

A

the offspring resulting from a cross between an organism with a homozygous dominant genotype, and one with a homozygous recessive genotyope

36
Q

define ‘F2 generation’

A

the offspring resulting from a cross between two F1 (heterozygous) organisms

37
Q

define ‘test cross’

A

a genetic cross in which an organism showing a characteristic caused by a dominant allele is crossed with an organism that is homozygous recessive; the phenotypes of the offspring can consequently be a guide to whether the first organism is homozygous or heterozygous

38
Q

define ‘linkage’

A

the presence of two genes that are on the same chromosome, so that they tend to be inherited together and do not assort independently

39
Q

define ‘gene mutation’

A

a change in the structure of a DNA molecule, producing a different allele of a gene

40
Q

what is a ‘silent mutation’

A

a mutation that has no apparent effect on an organism

Biology A-level (18 decks)

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