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biology > reproduction > Flashcards

reproduction Flashcards

1
Q

what is sexual reproduction?

A
  • type of reproduction
  • involves the production of gametes by meiosis
  • a gamete from each parent fuses to form a zygote
  • genetic information from each gamete is mixed so the resulting zygote is unique
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2
Q

what are gametes?

A
  • sex cells

- haploid

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3
Q

what is meiosis?

A
  • form of cell division involved in the formation of gametes in reproductive organs
  • chromosome number is halved
  • involves 2 divisions
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4
Q

what must occur prior to meiosis?

A

Interphase - copies of genetic information are made during this process

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5
Q

what happens during the first stage of meiosis?

A
  • chromosome pairs line up along the cell equator
  • the pair of chromosomes are separated and move to opposite poles of the cell.
  • chromosome number is halved
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6
Q

what happens during the second stage of meiosis?

A
  • chromosomes line up along the cell equator
  • the chromatids are separated and move to opposite poles of the cell
  • 4 unique haploid gametes are produced
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7
Q

why is meiosis important for sexual reproduction?

A
  • it increases genetic variation

- it ensures that the zygote formed at fertilisation is diploid

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8
Q

describe fertilisation and its resulting outcome

A

gametes join together to restore the normal number of chromosomes and the new cell then divides by mitosis. as the embryo develops, cells differentiate.

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9
Q

what is asexual reproduction?

A
  • type of reproduction
  • involves mitosis only
  • produces genetically identical offspring known as daughter cells.
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10
Q

describe the circumstances in which malarial parasites reproduce sexually and asexually

A
  • sexual reproduction in the mosquito

- asexual reproduction in the human host

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11
Q

describe the circumstances in which fungi reproduce sexually and asexually

A
  • asexual reproduction by spores

- sexual reproduction to give variation

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12
Q

describe the circumstances in which plants reproduce sexually and asexually

A
  • sexual reproduction to produce seeds

- asexual reproduction by runners or bulb division

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13
Q

what is DNA?

A

a double-stranded polymer of nucleotides, wound to form a double helix. this genetic material of the cell found in its nucleus.

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14
Q

define genome?

A

the entire genetic material of an organism

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15
Q

why is understanding the human genome important?

A

the whole human genome has been studied and is important for the development of medicine in the future.

  • searching for genes linked to different types of diseases
  • understanding and treating inherited disorders
  • tracing human migration patterns from the past
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16
Q

what is a chromosome?

A

a long, coiled molecule of DNA that carries genetic information in the form of genes

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17
Q

how many chromosomes do human body cells have?

A

46 chromosomes (23 pairs)

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18
Q

how many chromosomes do human gametes have?

A

23 chromosomes

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19
Q

define gene

A

a small section of DNA that codes for a specific sequence of amino acids when undergo polymerisation to form a protein

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20
Q

what are the monomers of DNA?

A

Nucleotides

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21
Q

what are DNA nucleotides made up of?

A
  • common sugar
  • phosphate group
  • one of 4 bases: A, T, C or G
22
Q

state the full names of the 4 bases found in nucleotides

A
  • Adenine
  • Thymine
  • Cytosine
  • Guanine
23
Q

describe how nucleotides interact to form a molecule of DNA

A
  • sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand
  • Base connected to each sugar
  • Complementary base pairs joined by weak hydrogen bonds.
24
Q

explain how a gene codes for a protein

A
  • a sequence of 3 bases in a gene forms a triplet
  • each triplet codes for an amino acid
  • the order of amino acids determines the structure and function of protein formed.
25
Q

why is the folding of amino acids important in proteins such as enzymes?

A

the folding of amino acids determines the shape of the active site which must be highly specific to the shape of its substrate

26
Q

what is protein synthesis?

A

the formation of a protein from a gene

27
Q

what are the 2 stages of protein synthesis?

A

1) Transcription

2) Translation

28
Q

what does transcription involve?

A

the formation of mRNA from a DNA template

29
Q

Outline transcription

A

1) DNA double helix unwinds
2) RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and moves along the DNA strand.
3) RNA polymerase joins free RNA nucleotides to complementary bases on the coding DNA strand.
4) mRNA formation complete. mRNA detaches and leaves the nucleus.

30
Q

what does translation involve?

A

A ribosome joins amino acids in a specific order dictated by mRNA to form a protein.

31
Q

outline translation

A

1) mRNA attaches to a ribosome
2) Ribosome reads the mRNA bases in triplets. Each triplet codes for 1 amino acid which is brought to the ribosome by a tRNA molecule.
3) A polypeptide chain is formed from the sequence of amino acids which join together

32
Q

what is a mutation?

A

A random change in the base sequence of DNA which results mostly in no change to the protein coded for, or genetic variants of the protein. Mutations occur continuously

33
Q

describe the effect of a gene mutation in coding DNA

A
  • if a mutation changes the amino acid sequence, protein structure and function may change.
  • if a mutation does not change amino acid sequence, there is no effect on protein structure or function.
34
Q

what is non-coding DNA?

A

DNA which does not code for a protein but instead controls gene expression

35
Q

describe the effect of a gene mutation in non-coding DNA

A

gene expression may be altered, affecting protein production and the resulting phenotype.

36
Q

where are the alleles?

A

different versions of the same gene

37
Q

what is a dominant allele?

A

a version of a gene where only one copy is needed for it to be expressed.

38
Q

what is a recessive allele?

A

a version of a gene where 2 copies are needed for it to be expressed

39
Q

what is meant when an organism is a homozygous?

A

when an organisation has 2 different versions of the same gene

40
Q

what is a genotype?

A

the genes present for a trait

41
Q

what is a phenotype?

A

the visible characteristic

42
Q

how are dominant alleles represented in a punnet square?

A

they are represented using uppercase letters.

43
Q

how are recessive alleles represented in a punnet square?

A

they use the lowercase version of the same letter as the dominant allele.

44
Q

what is the problem with single gene crosses?

A

most characteristics are controlled by multiple alleles rather than just one

45
Q

what is an inherited disorder?

A

a disorder caused by the inheritance of certain alleles.

46
Q

give 2 examples of inherited disorders

A
  • polydactyly - caused buy a dominant allele

- cystic fibrosis - caused by a recessive allele

47
Q

how are embryos screened for inherited disorders?

A

during IVF , one cell is removed and tested for disorder-causing alleles. If the cell doesn’t have any indicator alleles, then the originating embryo is implanted into the uterus

48
Q

what are the ethical issues concerning embryo screening?

A
  • it could lead to beliefs in society that being disabled or having a disorder is less human or associated with inferiority
  • the destruction of embryos with inherited disorders is seen by some as murder as these would go become human beings.
  • it could be viewed as part of the concept of designer babies as it may be for the parents convenience or wishes rather than the child’s wellbeing.
49
Q

what are the economic issues concerning embryo screening?

A

costs of hospital treatment and medication will need to be considered if it is known that a child will have an inherited disorder and financial support explored if necessary.

50
Q

what are the social issues concerning embryo screening?

A
  • social care for children with inherited disorder may need to be considered if parents are unable to provide care.
  • if an embryo is found to have an inherited disorder and is terminated, this can prevent a child and its parents from potential suffering in the future due to the disorder.
51
Q

what is gene therapy?

A

the insertion of a normal allele into the cells of a person with an inherited disorder to functionally replace the faulty allele.

52
Q

what are the ethical issues concerning gene therapy?

A
  • some people believe that it is going against and playing God.
  • the introduced genes could enter sex cells and so be passed to future generations

biology (7 decks)

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