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SB3 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does sexual reproduction produce?

A

Genetically different cells.

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2
Q

How many chromosomes do gametes contain?

A

Only half the number of a normal cells.

They’re haploid

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3
Q

What is sexual reproduction?

A
  1. It’s where genetic information from two organisms (a father and mother) is combined to produce offspring which are genetically different to either parent.
  2. The father and mother produce gametes (reproductive cells). In animals these are sperm and egg cells.
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4
Q

What happens at fertilisation?

A

A male gamete fuses with a female gamete to produce a fertilised egg, also known as a zygote.

The zygote ends up with the full set of chromosomes (so its diploid).

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5
Q

What happens to the zygote after fertilisation?

A

It then undergoes cell division (by mitosis) and develops into an embryo.

The embryo inherits characteristics from both parents as it has received a mixture of chromosomes (and therefore genes)from its mum and dad.

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6
Q

What’s a gamete?

A

Reproductive cell.

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7
Q

What’s a diploid cell?

A

Has a full set of chromosomes.

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8
Q

What’s a haploid cell?

A

Have half the number of chromosomes of normal cells.

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9
Q

What’s a zygote?

A

Fertilised egg.

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10
Q

How are gametes produced?

A

Meiosis

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11
Q

What is meiosis?

A

It’s a type of cell division.

It doesn’t produce identical cells like mitosis does.

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12
Q

Explain what happens in the first division of meiosis

A
  1. Before the cell starts to divide, it duplicates its DNA. One arm of each x shaped chromosome is an exact copy of the other arm.
  2. The chromosomes line up in pairs in the centre of the cell. One chromosome in each pair came from the organisms mother and one came from its father.
  3. The pairs are then pulled apart, so each new cell only has one copy of each chromosome. Some of the fathers and mothers chromosomes go into each new cell.
  4. Each new cell will have a mixture of the mothers and fathers chromosomes. Mixing up the genes like this is really important - it creates genetic variation.
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13
Q

Explain what happens in the second division of meiosis

A
  1. In the second division the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.
  2. Your get four haploid daughter cells - these are gametes. Each gamete only has a single set of chromosomes. The gametes are all genetically different.
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14
Q

What happens when cells reproduce asexually?

A

They divide by mitosis - this results in two diploid daughter cells, which are genetically identical to each other and to the parent cell.

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15
Q

What are the advantages of asexual reproduction?

A

Can produce lots of offspring very quickly because the reproductive cycle is so fast.
This can allow organisms to colonise a new area very rapidly.

Only one parent is needed - this means organisms can reproduce whenever conditions are favourable without having to wait for a mate.

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16
Q

What are the disadvantages of asexual reproduction?

A

There’s no genetic variation between offspring in the population, so if the environment changes and conditions become unfavourable, the whole population may be affected.

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17
Q

What are the advantages of sexual reproduction?

A

Creates genetic variation within the population, which means different individuals have different characteristics.
This means that if the environmental conditions change, its more likely that at least some individuals will have the characteristics to survive.

Over time this can end to natural selection and evolution, as species become better adapted to their new environment.

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18
Q

What are the disadvantages of sexual reproduction?

A

Takes more time and energy than asexual, so organisms produce fewer offspring in their lifetime.

Two parents are needed for sexual reproduction. This can be a problem if individuals are isolated.

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19
Q

What is DNA made up of?

A

Nucleotides.

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20
Q

What is DNA?

A

Its strands of polymers made up of lots of repeating units called nucleotides.

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21
Q

What do nucleotides consist of?

A

One sugar molecule.
One phosphate molecule.
One base.

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22
Q

What do the sugar and phosphate molecules do?

A

They form a backbone to the DNA strands.

They alternate.

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23
Q

What are the different bases?

A

A (adenine)
T (thymine)
C (cytosine)
G (guanine)

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24
Q

What shape is DNA?

A

Double helix.

Two strands coiled together in a spiral.

25
Q

What do bases join to?

A

One of four different bases join to each sugar.
Each base links to a base on the opposite stand in the helix.

A always pairs up with T.
C always pairs up with G.

26
Q

What are the base pairings called?

A

Complementary base pairing.

27
Q

What are base pairings joined together by?

A

Weak hydrogen bonds.

28
Q

What is DNA stored as?

A

Chromosomes

29
Q

What is a chromosomes?

A

Are long, coiled up molecules of DNA.

30
Q

What is a gene?

A

Is a section of DNA on a chromosome that codes for a particular protein.

31
Q

What’s a genome?

A

Genetic makeup.

All of an organisms DNA.

32
Q

What are proteins made up of?

A

Chains of molecules called amino acids.

33
Q

What’s a mutation?

A

Its a rare, random change to an organisms DNA base sequence that can be inherited.

34
Q

What are the two stages of how proteins are made?

A

Transcription

Translation

35
Q

What are the stages of transcription?

A
  1. RNA polymerase binds to a region of non-coding DNA in front of a gene.
  2. The two DNA strands unzip and the RNA polymerase moves along one of the strands of the DNA.
  3. Its uses the coding DNA in the gene as a template to make the mRNA. Base pairings between the DNA and RNA ensures that the mRNA is complementary to the gene.
  4. Once made, the mRNA molecule moves out of the nucleus and joins with a ribosome.
36
Q

What is transcription?

A

When a gene is to be expressed, the base sequence of DNA is copied or transcribed into mRNA (messenger RNA). This process takes place in the nucleus and occurs in a series of stages.

37
Q

What are the stages of translation?

A
  1. Amino acids are brought to the ribosome by another RNA molecule called transfer RNA (tRNA).
  2. The order in which the amino acids are brought to the ribosomes matches the order of the base triplets (codons) in mRNA.
  3. Part of the tRNA’s structure is called an anticodon - it is complementary to the codon for the amino acid.
    The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order.
  4. Amino acids are joined together by the ribosome. This makes a polypeptide.
38
Q

What happens after translation?

A

After translation, the polypeptide is finally folded into the correct shape and becomes a protein.

Peptide bonds form between the adjacent amino acids to finalise the structure.

39
Q

What did Mendel do genetic experiments with?

A

Pea plants

40
Q

What did Gregor Mendel discover?

A

On his garden plot at the monastery in the mid 19th century, he noted how characteristics in plants were passed on from one generation to the next.

41
Q

When were Mendel’s results published?

A

1866

They eventually became the foundation of modern genetics.

42
Q

What did Mendel do in one of his experiments?

A
  1. Mendel crossed two pea plants of different heights - a tall pea plant and a dwarf pea plant.
    The offspring produced were all tall pea plants.
  2. He then bred two of these tall offspring together.
    He found that when the offspring from the first cross were crossed with each other, three tall offspring were produced for every one dwarf offspring overall.

In other words, he produced a 3:1 ratio.
Tall was dominant (T) small was recessive (t)

43
Q

What were Mendel’s 3 important conclusions about heredity in plants?

A
  1. Characteristics in plants are determined by hereditary units.
  2. Hereditary units are passed on to offspring unchanged from both parents, one unit from each parent.
  3. Hereditary units can be dominant or recessive - if there is both recessive and dominant, dominant characteristics will be expressed.
44
Q

What are alleles?

A

Different versions of the same gene.

45
Q

How are alleles shown as dominant and recessive?

A

Capital letter

Lower case letter

46
Q

What does homozygous mean?

A

If an organism has two alleles for a particular gene that is the same.

E.g - AA or aa

47
Q

What does heterozygous mean?

A

If its two alleles for a particular gene are different.

E.g - Aa

48
Q

What is a genotype?

A

Its the combination of alleles you have.

Genetic makeup

49
Q

What is a phenotype?

A

Characteristics

50
Q

Why are men more likely to be colour blind?

A

Colour blindness is caused by a faulty allele carried on the X chromosome.
Women (XX) need two copies of the recessive allele, while men (XY) only need one copy.

A woman with only one recessive allele is a carrier.

51
Q

What are the four blood groups?

A

O, A, B, AB

52
Q

What are the 3 alleles for blood type?

A

I^O, I^A, I^B

53
Q

What does it mean by I^A and I^B being codominant with each other.

A

It means that when an individual has both of these alleles, then they’ll have the blood type AB - one allele isn’t dominant over the other one.

This mean I^O is recessive.

54
Q

What causes genetic variation within a species?

A

Its caused by organisms having different alleles.

This can then lead to different phenotypes.

55
Q

How can the environment affect variation?

A

E.g - plant by a window = green

Plant in darkness = yellow, tall and spindly.

56
Q

How do alleles arise?

A

They’re due to genetic mutations.

57
Q

Do mutations effect the phenotype?

A

They don’t always have a big effect on the phenotype, in fact most don’t have any effect (they’re neutral).

But some can have a small affect - e.g- long hair instead of short.

Very rarely, a single mutation will have a big effect - e.g- the production of a protein that is so different that it can no longer carry out its function.

58
Q

What is the human genome project?

A

Thousands of scientists from all over the world collaborated on the human genome project. The big idea was to find every single human gene.

Biology❌ (9 decks)

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