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S2 Biology > Genetics > Flashcards

Genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Where is genetic material (DNA) contained in the cell?

A

In the nucleus.

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2
Q

What does DNA stand for?

A

Deoxyribonucleic acid.

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3
Q

What is the structure of DNA?

A

A double helix.

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4
Q

What does the structure of DNA consist of?

A

Two anti-parallel strands made up of nucleotides which are twisted around each other into double helix.
Strands (backbone) held together by hydrogen bonds.

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5
Q

What is a nucleotide?

A

One unit of sugar, phosphate and base.

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6
Q

What are the four bases?

A

Adenine, thymine, guanine and cytosine.

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7
Q

What are the combinations for the four bases?

A

Adenine - thymine

Guanine - cytosine

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8
Q

What are these combinations referred to as?

A

Base pairings.

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9
Q

What is special about the sequence of bases along each chromosome in every individual?

A

It is unique to that individual. (Except with identical twins)

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10
Q

What is an allele?

A

One of two possible versions of a particular gene.

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11
Q

What are chromosomes?

A

Genetic structure usually occurring in functional pairs in nucleus of cells. (Except gametes and bacteria)

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12
Q

What is a diploid?

A

Normal number of chromosomes in cells of an organism.

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13
Q

What is DNA?

A

Molecule that forms genes and chromosomes.

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14
Q

What is a double helix?

A

3-dimensional structure of DNA.

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15
Q

What is a gene?

A

Short section of DNA on a chromosome that codes for a characteristic.

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16
Q

What is a genome?

A

Entire genetic material of an organism.

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17
Q

What is a haploid?

A

Cell or nucleus with half the normal number of chromosomes.

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18
Q

What is the base triplet hypothesis?

A

The correct base triplets are arranged in correct sequence along coding strand of DNA that code for particular amino acid.

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19
Q

What is protein synthesis?

A

After amino acids are coded they are linked together to form proteins, e.g. enzymes.

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20
Q

How does DNA code for protein?

A

Along coding strand each base triplet codes for 1 amino acid.
Sequence of bases determines which amino acids are produced.
Amino acids are building blocks of proteins.
Sequence of amino acids determines protein made.

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21
Q

What is mitosis?

A

Those of cell division that produces cells genetically identical to parent cell and each other.

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22
Q

Where does mitosis take place?

A

Throughout the body.

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23
Q

What is mitosis important for?

A

Growth.
Replacing worn out cells.
Repairing damaged cells.

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24
Q

What does mitosis ensure in new daughter cells?

A

Have exactly same chromosome as each other and parent cell.

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25
Q

What happens during mitosis?

A
  1. Each chromosome duplicates by splitting lengthwise into two identical chromosomes held together by centromere.
  2. Original and duplicate chromosomes line up along equator of cell.
  3. Original chromosome and duplicate separate and pulled to opposite ends of cell.
  4. Once they reach opposite ends of cell, cell divides in two.
  5. Two new daughter cells contain exactly same chromosomes as each other and parent cell.
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26
Q

Where does meiosis occur in the body?

A

In sex organs (testes and ovaries).

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27
Q

What does meiosis produce?

A

Gametes.

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28
Q

What type of division is meiosis?

A

Reduction division as produces gametes half number of chromosomes (haploid) as other cells (diploid) - ensures when gametes fuse in fertilisation Nora l diploid number is restored.

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29
Q

What does 1 cell produce in meiosis?

A

4 genetically different haploid cells in 2 divisions.

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30
Q

What is independent assortment?

A

Process where chromosomes are resorted randomly during meiosis to produce gametes.

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31
Q

What happens before meiosis begins?

A

All chromosomes duplicate to form 2 chromatids.
Cells undergo 2 rounds of division.

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32
Q

What happens during the first division in meiosis?

A
  1. Homologous pairs of chromosomes align in middle of parent cell and are separated.
  2. Cell divides so each new daughter cell only contains 1 chromosome from each pair, 23 chromosomes in total.
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33
Q

What happens during the second division in meiosis?

A
  1. In each cell, chromosomes align in centre and chromatids are pulled apart into separate halves of cell.
  2. Each cell divides again, so each new cell only contains one chromatid from each chromosome.
34
Q

What is a reduction division?

A

1 cell producing 4 genetically different, haploid daughter cells.

35
Q

What is fertilisation?

A

Fusion of gametes to form zygote, restores diploid number.

36
Q

What is a genotype?

A

Genetic makeup of organism for a characteristic or characteristics. (Represent by letter, e.g. BB, Bb, bb).

37
Q

What is heterozygous?

A

Two alleles for characteristics are different - 1 dominant, 1 recessive. (Bb)

38
Q

What is homozygous?

A

Two alleles for particular gene are the same. (BB, bb)

39
Q

What is a pedigree diagram?

A

Diagram that shows how particular condition is inherited through different generations in a family.

40
Q

What is a phenotype?

A

Outward appearance of an individual. (Brown or blue eyes)

41
Q

What is a Punnett square?

A

Grid used to work out possible offspring in genetic cross.

42
Q

What does recessive mean?

A

Allele that will only show a characteristic if both alleles are recessive. Masked by dominant allele.

43
Q

What is a monohybrid cross?

A

Cross involving one characteristic, e.g. eye colour.

44
Q

What is a genetic cross used for?

A

To work out offspring produced from 2 heterozygous parents.

45
Q

What is a test cross used to determine?

A

An unknown genotype.
Determine genotype of dominant phenotype.

46
Q

Why is a test cross used to determine the genotype for a dominant phenotype?

A

Individuals are either homozygous dominant or heterozygous.

47
Q

How is a test cross used to determine the genotype of a dominant phenotype individual?

A

Individual crossed with homozygous recessive individual.
If individual is homozygous dominant, all offspring will have same phenotype.
If individual is heterozygous, 50% offspring will have homozygous recessive phenotype.

48
Q

What are the sex chromosomes?

A

23rd pair of chromosomes in a human karyotype.

49
Q

What does the male sex chromosome consist of?

A

Half male’s sperm will have Y chromosome and half will have X chromosome.

50
Q

What does the female sex chromosome consist of?

A

All female eggs (ovum) will have X chromosome.

51
Q

What happens with the sex chromosomes during fertilisation?

A

Equal chance zygote produced will be XX or XY.

52
Q

What can sex chromosomes carry?

A

Alleles.

53
Q

What is the difference between the X and Y chromosomes?

A

Y chromosome does not contain any alleles compared to X chromosome.

54
Q

What occurs if the X chromosome in a male has a recessive allele?

A

Cannot be masked by dominant allele on Y chromosome so shows in phenotype.

55
Q

What sex chromosomes do males have?

A

XY.

56
Q

What sex chromosomes do females have?

A

XX.

57
Q

What happens when 1 allele in an X chromosome is recessive in a female?

A

Can be masked by dominant allele on other X chromosome.

58
Q

What is a carrier?

A

Individuals who are heterozygous for a condition.
Carry harmful gene but don’t have condition.

59
Q

What are some examples of sex-linked conditions/genetic diseases?

A

Down syndrome
Cystic fibrosis
Haemophilia
Huntington’s disease
Red-green colour blindness

60
Q

What are the causes of Down syndrome?

A

Mutation.
Egg cell contains 24 chromosomes instead of 23.
Individual has 47 chromosomes instead of 46.
3 chromosomes at position 21.

61
Q

What are the effects of Down syndrome?

A

Reduced muscle tone.
Reduced cognitive development.

62
Q

What are the causes of cystic fibrosis?

A

Inherited.
Recessive allele.
Affected individual is homozygous recessive.

63
Q

What are the effects of cystic fibrosis?

A

Frequent and serious lung infections.
Problems digesting food.

64
Q

What are the causes of haemophilia?

A

Inherited.
Recessive allele.
Sex-linked.
More males affected than females.

65
Q

What are the effects of haemophilia?

A

Problem with blood clotting.
Risk of excessive bleeding from wound or bruising.

66
Q

What are the causes of Huntington’s disease?

A

Inherited.
Dominant allele.

67
Q

What are the effects of Huntington’s disease?

A

Affects nerve cells in brain, leading to brain damage.
Becomes apparent in middle age.
Fatal.
No cure.

68
Q

What are the causes of red-green colour blindness?

A

Inherited.
Recessive allele.
Sex-linked.
More males effected than females.

69
Q

What are the effects of red-green colour blindness?

A

Can’t see red or green tones.
Have difficulty making out differences in pale shades.
Tend to confuse orange and red.

70
Q

What is genetic screening used for?

A

To identify presence of genetic condition in foetus such as Down syndrome and cystic fibrosis.

71
Q

What is a type of genetic screening?

A

Amniocentesis.

72
Q

What happens during amniocentesis?

A
  1. Foetal cells removed from amniotic fluid in amnion (uterus).
  2. Long needle inserted into amnion.
  3. Foetal cells grown in lab and number of chromosomes counted.
73
Q

What is the risk of a miscarriage during amniocentesis?

A

1% risk.

74
Q

Who is amniocentesis used with?

A

Pregnant women who have greater risk of having child with genetic condition.

75
Q

How is the blood test for Down syndrome different from amniocentesis?

A

Less precise but poses no risk.

76
Q

What are the reasons someone would say yes to aborting a foetus if it has a genetic condition?

A

Child would have poor quality of life.
Expense of time with their other children.

77
Q

What are the reasons someone would say no to aborting a foetus if it has a genetic condition?

A

Unborn child doesn’t have a say.
Not morally right to ‘kill’ a foetus.
Banned in some religions and countries.

78
Q

What are the ethical issues surrounding aborting a foetus with a genetic condition?

A

Who decides on who should be screened?
Is there an acceptable risk associated with genetic screening?
Costs of screening compared with costs of treating individuals with genetic condition - should cost be a factor?

79
Q

What are the reasons for information from genetic screening being made public?

A

Could help with medical research.

80
Q

What are the reasons against information from genetic screening being made public?

A

Insurance companies may not give life insurance or could be more expensive.

S2 Biology (3 decks)

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