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Biology > B5 > Flashcards

B5 Flashcards

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1
Q

Gametes?

A

one type of cell where the chromosomes are not paired. For example, in humans the gametes are sperm and egg cells

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2
Q

How are gametes made?

A

By a type of cell division called meiosis

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3
Q

fusion?

A

joining e.g. sexual reproduction involves fusion of male and female gametes

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4
Q

What happens in asexual reproduction?

A

There is only one parent therefore it does not involve Gametes. there is also no mixing of genetic information due to there only being one parent, so all offspring are identical

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5
Q

where is the only place that meiosis takes place?

A

reproductive organs e.g. testes and ovaries

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6
Q

meiosis?

A

cells very carefully count and divide their chromosomes so that each gamete has exactly 23 chromosomes. Then when an egg with its 23 chromosomes is fertilized by a sperm with its 23 chromosomes, the resulting fertilized egg has exactly 46 chromosomes.

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7
Q

Fertilisation?

A

gametes joining together in sexual reproduction

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8
Q

What has happened to the cells due to fertilisation?

A

The cell now has the normal number of chromosomes

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9
Q

What happens after fertilisation?

A

The new cell divides by mitosis to produce a clump of identical cells (embryo)

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10
Q

What happens as the embryo develops?

A

the cells differentiate forming different cell types e.g. muscle cells, brain cells

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11
Q

What does our DNA determine?

A

our inherited features

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12
Q

What is a key feature of DNA?

A

has two polymers forming a double helix

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13
Q

Gene?

A

Small section of DNA on a chromosome

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14
Q

Genome?

A

The entire genetic material of an organism

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15
Q

3 reasons why is it good that scientists have studied the entire human genome?

A

1) help us to search for genes that are linked to a disease

2) help us to understand and treat inherited disorders

3) helps to discover ancestry

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16
Q

How many copies of each gene do we have?

A

2

17
Q

Alleles?

A

Versions of a gene

18
Q

Genotype?

A

Tells us the alleles present

19
Q

Homozygous?

A

The person has got two copies of the same allele e.g. EE or ee

20
Q

Phenotype?

A

tells us the characteristics caused by the persons alleles

21
Q

Heterozygous?

A

The person have two different alleles
e.g. Ee or Dd

22
Q

What phenotype will a person with heterozygous have?

A

The dominant allele e.g. polydactyly e.g. not cystic fibrosis

23
Q

Recessive allele?

A

Will only show in the phenotype if two copies are present e.g. the other allele is dominant

24
Q

What is Cystic fibrosis?

A

a disorder of cell membranes

25
Q

Is a defective cell membrane dominant or recessive?

A

recessive, therefore, in order to have cystic fibrosis, the person has to have two copies of the defective allele (both parents have to have it)

26
Q

What happens if a cystic fibrosis person has a Cc allele?

A

They are a carrier

27
Q

what is wrong with people that have polydactyly?

A

extra fingers or toes

28
Q

What happens if on of the embryo’s parents has a dominant allele of polydactyly?

A

They will have the disorder because polydactyly is a dominant allele

29
Q

Embryo screening?

A

embryos are tested to see if they have the alleles for inherited disorders

30
Q

2 problems with embryo screening?

A

Expensive - ppl say it should be spent elsewhere in the health service

the best embryo is chosen and the rest are destroyed - healthy or unhealthy, therefore ppl say it is unethical

31
Q

What could happen in the future with embryo screening?

A

May be able to screen embryos to produce offspring with desirable features e.g. taller, intelligent

32
Q

What is the person called if they only have one allele of cystic fibrosis?

A

A carrier

33
Q

What is the chance that 2 people who are carriers of cystic fibrosis have a baby which has the disorder?

A

25%

34
Q

What sex chromosomes do males have?

A

XY

35
Q

What sex chromosomes do females have?

A

XX

Biology (4 decks)

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