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Biology PMT > 6.1 Reproduction > Flashcards

6.1 Reproduction Flashcards

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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 (sperm cells and egg cells in animals, pollen, and egg cells in flowering plants.)
  • Haploid (Half the number of chromosomes).
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3
Q

What is meiosis?

A
  • Form of cell division involved in the formation of gametes (non - identical haploid cells) in reproductive organs.
  • Chromosomes number is halved.
  • Involves two 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
  • Chromosomes pairs line up along the cell equator.
  • The pair of chromosomes are separated and move to opposite poles of the cell (the side to which each chromosome is puled is random, creating variation).
  • 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.

Four unique haploid gametes are produced.

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7
Q

Why is meiosis important for sexual reproduction? (2)

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 than divides by mitosis (which increases the number of cells)

As the embryo develops, cells differentiate.

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9
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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10
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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11
Q

Describe the circumstances in which plants reproduce sexually and asexually

A

Sexual reproduction to produce seeds.

Asexual reproduction by runners (e.g. strawberry plants) or bulb division (e.g. daffodils)

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12
Q

What is DNA

A

A double-stranded polymer of nucleotides, wound to form a double helix.

The genetic material of the cell found in the nucleus.

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13
Q

Define genome.

A

The entire genetic material of an organism

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14
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 disease.
  • Understanding and treating inherited disorders
  • Tracing human migration patterns from the past
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15
Q

What is a chromosome?

A

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

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16
Q

How many chromosomes do human body cells have?

A

46 chromosomes (23 pairs)

17
Q

How many chromosomes do human gametes have?

A

23 chromosomes

18
Q

Define gene

A

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

19
Q

What are alleles

A

Different version of the same gene.

20
Q

What is a dominant allele

A

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

21
Q

What is a recessive allele?

A

A version of a gene where two copies are needed for it to be expressed.

22
Q

What is meant when an organism is homozygous?

A

When an organism has two copies if the same allele (two recessive of two dominant).

23
Q

What is meant when an organism is heterozygous?

A

When an organism has two different versions of the same gene (one dominant and one recessive)

24
Q

What is the genotype?

A

The genes present for a trait.

25
Q

What is the phenotype?

A

The visible characteristic.

26
Q

How are dominant alleles represent is a Punnett square?

A

They are represented using uppercase letters

27
Q

How are recessive alleles represented in a Punnett square

A

They use the lowercase version of the same letter as the dominant allele

28
Q

What is the problem with single gene crosses?

A

Most characteristics are controlled by multiple alleles rather than just one

29
Q

What is an inherited disorder?

A

A disorder caused by the inheritance of certain alleles.

30
Q

Give 2 examples of inherited disorders.

A

Polydactyl (having extra fingers or toes) - caused by a dominant allele.

Cystic fibrosis (A disorder of cell membranes) - caused by a recessive allele

31
Q

How are embryos screened for inherited disorders?

A

During IVF, one cell is removed (from an 8 cell embryo) and tested for disorder-causing alleles. If the cell doesn’t have an indicator alleles, then the originating embryo is implanted into the uterus.

32
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 on to become human beings.
33
Q

What are the economic issues concerning embryo screening?

A

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

34
Q

What are the social issues concerning embryo screening?

A

Social care for children with inherited disorders may need to be considered if parents are unable to provide care

If an embryo is found to have a inherited disorder and is terminated, this can prevent a child and its parents from potential suffering in the future due to the disorder.

35
Q

What is gene therapy?

A

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

36
Q

What are some ethical issues concerning gene therapy ?

A

Some people believe that is going against and ‘playing god’

The introduced genes could enter sex cells and so be passed to future generations.

37
Q

What are sex chromosomes?

A

A pair of chromosomes that determine sex:

  • Males = X & Y chromosomes
  • Females = X & X chromosomes
38
Q

What is a sex-linked characteristics?

A

A characteristics that is coded for by and allele found on a sex chromosome

Biology PMT (24 decks)

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