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GCSE CCEA Biology unit 2 And 3 > The Genome, Chromosomes, DNA And Genetics > Flashcards

The Genome, Chromosomes, DNA And Genetics Flashcards

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1
Q

what is a chromosome?

A

A long strand of DNA located in the nucleus

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2
Q

What is a gene? (2)

A
  • A short strand of DNA (part of a chromosome)
  • that codes for a particular characteristic
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3
Q

What is an allele?

A
  • An alternative form of gene
  • for a particular characteristic
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4
Q

Define Gene Locus

A

The position of a gene on a chromosome

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5
Q

What is independent assortment? (3)

A
  • A process that takes place during meiosis
  • in which chromosomes are reassorted
  • in the formation of gametes
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6
Q

What is meiosis? (3)

A
  • A type of cell division
  • that produces cells (gametes)
  • that have half the normal chromosome number (haploid cells)
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7
Q

What is mitosis? (3)

A
  • A type of cell division
  • that produces cells genetically identical
  • to the parent cell and each other
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8
Q

What is the genotype of an allele?

A
  • The genetic arrangement of alleles (genetic make up)
  • for 1 or more traits
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9
Q

What is meant by phenotype? (2)

A
  • The actual appearance of alleles (genetic make up)
  • for 1 or more traits
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10
Q

What is meant by the term homozygous?

A

if the individual has two identical alleles for a characteristic

e.g. AA or aa

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11
Q

What is meant by the term heterozygous?

A

If the individual has two different alleles for a characteristic

E.g. Aa

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12
Q

What is meant by the term recessive?

A

The allele that is only expressed in the homozygous form

E.g. aa

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13
Q

What is meant by the term dominant?

A

The allele that is expressed in both the homozygous and heterozygous forms

E.g. AA or Aa

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14
Q

What is heredity? (2)

A
  • The transfer of genetic information (alleles)
  • from one generation to the next
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15
Q

What are homologous chromosomes? (3)

A
  • A pair of chromosomes
  • that are the same length
  • and have genes for the same characteristics

(The alleles present may be different)

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16
Q

What is monohybrid inheritance?

A

When only one trait (gene) is considered in a genetics cross

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17
Q

What is a back/test cross? (2)

A
  • a test carried out to confirm the genotype of an individual
  • with a pure bred homozygous recessive

(I.e. to determine if the individual is heterozygous or homozygous dominant)

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18
Q

What are the stages of meiosis? (2)

A
  • where one cell divides into two
  • the two cells divide to form a total of four cells
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19
Q

What is a genetic disorder? (2)

A
  • A disease caused by errors in a DNA sequence,
  • disorders are heritable so can potentially be passed on to offspring
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20
Q

What is Cystic Fibrosis? (2)

A
  • A genetic disorder of the cell membranes that leads to excess mucus that damages organ systems,
  • caused by a recessive allele
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21
Q

How is cystic fibrosis inherited?

A

only if two recessive alleles are present

22
Q

What is a carrier? (2)

A
  • An individual who carries a recessive allele for a disorder
  • but does not express the disorder’s phenotype
23
Q

What is haemophilia? (2)

A
  • An inherited condition characterised by an inability to clot blood
  • haemophilia is a sex-linked condition
24
Q

How is haemophilia inherited? (2)

A
  • it is a sex-linked disorder, meaning it is found on the X-chromosome
  • It takes two of the allele for a woman to get the disorder, but only one is required for a male
25
Q

What are sex-linked disorders? (2)

A
  • A genetic condition caused by genes on the 23rd chromosomes or the X or Y chromosome
  • they only require one copy of an allele for male inheritance, but two for females
26
Q

What is Huntington’s disease? (2)

A
  • A genetic disorder that causes progressive deterioration of brain cells,
  • does not appear until older age
27
Q

How is Huntington’s disease inherited? (2)

A

It is expressed by a dominant allele, it will always be expressed unless an individual is homozygous recessive
- you cannot be a carrier for dominant disorders

28
Q

What is Down syndrome?

A

A condition of intellectual disability and associated physical disorders

29
Q

How is Down syndrome inherited? (2)

A
  • Caused by a genetic trait known as trisomy, where an additional copy of the 21st chromosome is present,
  • it results from an extra chromosome to make a total of 47 rather than 46
30
Q

What are the X and Y chromosomes?

A
  • the 23rd pair of chromosomes in a human,
  • the combination of these determines the sex of an offspring
31
Q

What gender is given by XX

What is the probability of them having a XX child?

A
  • female
  • 50%
32
Q

What gender is given by XY

What is the probability of them having a XY child?

A
  • male
  • 50%
33
Q

How many chromosomes are in human cells? How are they arranged?

A

46 —> in 23 pairs

34
Q

How many chromosomes are in human gametes?

A

23
(Half the normal number)

35
Q

How is insulin produced? (8)

A
  • use restriction enzyme to remove human insulin gene
  • remove plasmid from bacterium
  • cut plasmid open using restriction enzyme
  • implant insulin gene into plasmid
  • put plasmid into bacterium
  • place bacteria in fermenter with optimum pH, temp, nutrients etc.
  • bacteria reproduce
  • downstreaming: extract, purify and pack insulin
36
Q

Describe how the insulin gene can be incorporated into the plasmid (3)

A
  • restriction enzyme cuts insulin gene from human DNA
  • same restriction enzyme cuts plasmid open
  • insulin gene joins plasmid due to complementary sticky ends
37
Q

What is the structure of DNA?

A

Double Helix

38
Q

What is meant by the genome of an organism?

A

All the DNA in an organism

39
Q

what are the three components of DNA - what are they represented with in diagrams?

A
  • phosphates - circles
  • sugars - pentagons
  • bases - blocks with names
40
Q

What are the 4 bases? Which link together?

A
  • adenine
  • thymine
  • cytosine
  • guanine

AT
CG

41
Q

What connects bases in DNA?

A

Hydrogen bonds

42
Q

What term describes a phosphate, sugar and base

A

A nucleotide

43
Q

What is a base triplet? (2)

A
  • The sequence of three bases on a single strand of DNA
  • that codes for an amino acid
44
Q

What are the three uses of Mitosis?

A
  • growth
  • repair of damaged tissue
  • replacing worn out cells
45
Q

What is genetic engineering? (2)

A
  • A process that modifies the genome of an organism
  • to introduce desirable characteristics
46
Q

Where are restriction enzymes used? How do they cut? (2)

A
  • In extraction of the human insulin gene and cutting open a bacterial plasmid
  • they leave sticky ends for the other gene to bond
47
Q

What is Amniocentesis? (2)

A
  • The extraction of foetal cells from amniotic fluid (by a needle) for examination,
  • to test for genetic abnormalities
48
Q

name two sex-linked disorders

A
  • colour blindness
  • haemophilia
49
Q

What is the name of cells with half the number of chromosomes?

A

Haploid cells

50
Q

What is the name of cells with a normal number of chromosomes?

A

Diploid cells

51
Q

How does the DNA of individuals differ?

A

Each person has different base sequences

52
Q

What are karyotypes?

A

An individual’s complete set of chromosomes

GCSE CCEA Biology unit 2 And 3 (7 decks)

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