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Biology > B6 - Inheritance, Variation & Evolution > Flashcards

B6 - Inheritance, Variation & Evolution Flashcards

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1
Q

What are chromosomes?

A

Long molecules of DNA. They determine what characteristics you have, they normally come in pairs and are in the nucleus

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2
Q

Deoxyribonucleic acid means what?

A

DNA

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3
Q

This is a polymer, made of 2 strands coiled in a double helix. What is this?

A

DNA

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4
Q

What does a gene do?

A

Codes for a specific protein - it is a small section of DNA found on a chromosome that tells the cell to make a particular sequence of amino acids, which forms a specific protein.
Only 20 amino acids are used, but they make thousands of different proteins

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5
Q

What determines what type of cell it is?

A

The proteins that the cell produces, as told by the genes in DNA

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6
Q

Every organism has a genome, but what does that mean?

A

A genome is the fancy term for the entire set of genetic material in an organism

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7
Q

How does knowing the human genome (which scientists now do) help?

A

1) Allows scientists to identify gnes in the genome that are linked to different types of diesease
2) Knowing which genes are linked to inherited diseases could help us understand them better and could help us develop effective treatments for them
3) Scientists can trace migration of certain populations of people around the world. All modern humans are descended from a common ancestor from Africa, but are now all over the planet. The human genome is mostly identical in all individuals, but as different populations of people migrated away from Africa, they gradually developed tiny differences in their genome. Investigating these, and scientists can work out when new populations split off in a different direction, and what route they took

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8
Q

Which types of reproduction produces genetically different cells?

A

Sexual reproduction - where the genetic information from 2 organisms (father and mother) is combined to produce offspring genetically different to either parent

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9
Q

How many chromosomes does a human gamete contain?

A

23 - half the number of chromosomes in a normal cell (a normal human cell has 23 PAIRS, a gamete has 23 individual ones, no pairs)

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10
Q

Give examples of human gametes

A

Sperm cells and egg cells

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11
Q

What is fertilisation (animals)?

A

When the egg (from the mother) and sperm (from the father) fuse together to form a cell with the full number of chromosomes (half from the mother, half from the father)

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12
Q

Give the scientific definition of sexual reproduction

A

It involves the fusion of male and female gametes. Because there are 2 parents, the offspring contain a mixture of their parents’ genes

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13
Q

Why does the offspring from sexual reproduction inherit features from both parents?

A

Because it has received a mixture of chromosomes from both parents, and the chromosomes determine the offspring’s features. Half from mother, half from father

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14
Q

What does asexual production do?

A

It produces genetically identical cells - there’s only one parent, so the offspring are genetically identical to that parent

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15
Q

How does asexual reproduction occur?

A

Through mitosis, as there is only one parent so no fusion of gametes. An ordinary cell makes a new on by dividing in two.
The new cell has exactly the same genetic information as the parent cells - it is a clone

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16
Q

Which of these methods of reproduction produces a clone?

a) Sexual reproduction
b) Asexual reproduction

A

b) Asexual reproduction, as the one parent reproduces with mitosis - genetically identical

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17
Q

Give some examples of things that reproduces

a) Sexually
b) Asexually

A

a) Most animals, humans

b) Bacteria, some plants and some animals (star fish)

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18
Q

What are gametes?

A

A cell with half the amount of chromosomes a normal cell has. They are produced by meiosis, so that when the sperm and egg cells fuse together in humans again, they form one complete cell

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19
Q

Talk through the stages of meiosis

A

1) Before the cell starts to divide, it duplicates it’s genetic information stored in the DNA, forming 2 armed chromosomes. One arm of each chromosomes is an exact copy of the other. After replication, they rearrange themselves into pairs
2) In the first division, the chromosome pairs line up in the centre of the cell
3) The pairs are pulled apart, so the 2 new cells only have one copy of each chromosome. Some of the father’s and some of the mother’s are in each cell.
4) In the 2nd division, teh chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart again
5) There are now 4 gametes, each with only a single set of chromosomes in it. Each gamete is genetically different from the others, as the chromosomes all get shuffled up during meiosis and each gamete only gets half of them randomly

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20
Q

How many gametes are produced at the end of meiosis?

A

4

21
Q

What does the cell produced by gamete fusion do?

A

It replicates itself.
After 2 gametes have fertilised, the new cell divides by mitosis to make a copy of itself. It does this many times to produce an embryo
As the embryo develops, these cells start to differentiate

22
Q

What happens as an embryo develops, after the original gamete fusion has replicated lots with mitosis?

A

The cells start to differentiate to form the different types of specialised cells that make up a whole organism

23
Q

What controls your sex?

A

Your chromosomes - X and/or Y ones

24
Q

Which of these chromosome pairs means you’re female?

a) XX
b) XY
c) YX
d) YY

A

a) XX

25
Q

Which of these chromosome pairs means you’re male?

a) XX
b) XY
c) YX
d) YY

A

b) XY

26
Q

What female/ male chromosomes do human gametes have?

A

Egg cell - XX - female

Sperm cell - XY - male

27
Q

Prove that there is a 50% chance of having a female or male child

A

A sperm cell (XY) and an egg cell (XX) fuse together. Drawing this info in a Punnett square:
X X
xx xx X - half are XX, so 50% female
xy xy Y - half are XY, so 50% male

(caps is from gametes, lower case what got. All should be caps, this is just to make it clearer looking at it)

28
Q

What does a Punnett square do?

A

Shows all the possible combinations of chromosomes, from there you can predict the probability of certain characteristics

29
Q

What do genes that you inherit control?

A

What characteristics you develop - female or male, hair colour eye colour, etc

30
Q

Give some examples of characteristics controlled by a single gene

A

Mouse fur colour
Red-green colour blindness in humans

However most characteristics are controlled by sevral genes interacting

31
Q

All genes exist in different alleles. These are the letters written into genetic diagrams. True or false?

A

True

32
Q

How do genes exist in different versions?

A

They are called alleles

33
Q

How many alleles do you have in your body?

A

You have 2 alleles of every gene in your body - one on each chromosomes in a pair

34
Q

Explain:

a) Homozygous
b) Heterozygous

A

a) When an organism has 2 alleles for a particular gene that are the same, it’s homozygous for that trait
b) When an organism has 2 alleles for a particular gene that are different

35
Q

What happens when 2 different alleles are present for the same gene - heterozygous?

A

Only one determines the characteristic present. The allele for the characteristic shown is the dominant allele (shown with a capital letter). The other allele is recessive, as it does not show (shown with a lowercase letter)
The dominant allele overrules the recessive one

36
Q

What is your genotype?

A

The combination of all the alleles that you have

Your alleles work at a molecular level to determine what characteristics you have - phenotype

37
Q

What does phenotype mean?

A

The physical characteristics you have, that you can see. Determined by your dominant alleles

38
Q

Are these alleles for genetics dominant or recessive?

a) Polydactyly
b) Cystic fibrosis

A

a) Dominant - D

b) Recessive - f

39
Q

What is cystic fibrosis?

A

A genetic disorder of the cell membranes. It reduces in teh body producing a lot of thick sticky mucus in the air passages and pancreas

40
Q

What is polydactyly?

A

A genetic disorder when a baby is born with extra fingers or toes. Not life threatening

41
Q

Give the alleles for polydactyly and cystic fibrosis

A

Polydactyly - D (dominant)

Cystic fibrosis - f (recessive)

42
Q

Embryos can be screened, but what does that do?

A

Sees if they have genetic disorders

43
Q

How can an embryo be screened?

A

In IVF (in vitro fertilisation), embryos fertilised in a lab then implanted back into the mothers womb can have a cell removed and studied.
MAny genetic disorders can be detected this way.
Also possible to get DNA from an embryo in the womb to test for disorders

44
Q

Give reasons

a) For embryonic screening
b) Against embryonic screening

A

a) It will help stop people suffering (quality of life>life), Treating disorders costs the Government & taxpayers a lot, Laws to stop it going too far with designer babies - at the moment parents can’t choose the sex of their baby (unless health reasons)
b) Implies people with genetic problems are undesirable which could increase prejudice, May come a point when people screen their embryos and pic the child they want to have, EXPENSIVE

45
Q

WHat are mutations?

A

Changes to the genome - a rare and random change in an organism’s DNA that can be inherited.

46
Q

WHat are alleles?

A

Genetic variants - all genes have 2 each, either the same, or one dominant

47
Q

ORganisms of teh same species look different, what is this called?

A

Variation

48
Q

An organisms genes are…

A

Inherited from its parents

49
Q

Variation can be what?

A

Genetic - caused by differences in genotype

Biology (17 decks)

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