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A Level Biology > Genetics and Cell Division > Flashcards

Genetics and Cell Division Flashcards

- DNA and protein synthesis - RNA and protein synthesis - Mutations - Chromosomes - Cell division (mitosis) - Cell division (meiosis)

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1
Q

What is DNA made up of?

A

Nucleotides containing bases. DNA has four different bases: Adenine (A), Cytosine (C), Guanine (G), Thymine (T)

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2
Q

What does Adenine (A) bond to?

A

Thymine (T)

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3
Q

What does Cytosine (C) bond to?

A

Guanine (G)

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4
Q

What does Guanine (G) bond to?

A

Cytosine (C)

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5
Q

What does Thymine (T) bond to?

A

Adenine (A)

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6
Q

Why does A bond with T and C bond with G?

A

These pairs are complementary bases. They join together because they complement each other in shape - this is called complementary base pairing.

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7
Q

What is the name given to the double-stranded structure of DNA?

A

Double helix

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8
Q

How many different bases are there in DNA?

A

4

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9
Q

Give the names of the bases in DNA.

A

Adenine, cytosine, guanine, thymine

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10
Q

How do the strands of DNA stay together?

A

Each base forms hydrogen bonds to a base on the other strand.

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11
Q

What is complementary base pairing?

A

This is when pairs of complementary bases join together. A pairs with T and C pairs with G.

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12
Q

What is a gene?

A

A section of DNA that codes for a specific protein.

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13
Q

What determines the order of amino acids in a protein?

A

The order of bases in the gene.

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14
Q

What is needed to make proteins?

A

RNA

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14
Q

In RNA there is no thymine (T). What base replaces it?

A

Uracil (U)

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15
Q

*Why does a copy of a gene need to be made for protein synthesis? *

A

Because the DNA molecule containing the gene is in the nucleus and is too big to leave the nucleus. But protein synthesis takes place in the cytoplasm, so a copy of the gene that is smaller and can leave the nucleus needs to be made.

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16
Q

What does the ‘m’ in mRNA stand for?

A

Messenger

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17
Q

In RNA, which base is complementary to adenine?

A

Uracil

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18
Q

Give the mRNA sequence that would be complementary to the DNA sequence: ATTGCGCA

A

UAACGCGU

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19
Q

What is a triplet?

A

Three bases in a row e.g. ACC

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20
Q

What do three bases in a row code for?

A

One amino acid

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21
Q

What is a mutation?

A

A change to the base sequence of DNA

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22
Q

How many bases code for one amino acid?

A

Three

22
Q

Mutations happen spontaneously, but how frequently they happen can be increased by what?

A

Mutagenic agents - factors that increase mutations, e.g. UV radiation in sunlight.

23
Q

What can a change in amino acid cause?

A

A different protein to be formed

24
Q

What are mutations?

A

Changes to the base sequence of DNA

25
Q

What do mutagenic agents do?

A

Increase the frequency of mutations.

26
Q

Where is DNA found?

A

In chromosomes

27
Q

What does each side of the ‘X’ referred to as?

A

A chromatid and the bit in the middle where they are attached is called the centromere

28
Q

How many pairs of chromosomes do humans have?

A

23 pairs (46 in total)

29
Q

How are human chromosomes found?

A

In pairs

30
Q

Where is most DNA found in a eukaryotic cell?

A

In the nucleus

31
Q

How many homologous pairs of chromosomes do human cells have?

A

23

32
Q

Are homologous pairs of chromosomes identical. Explain your answer.

A

No. with the exception of the sex chromosomes, they are the same size and carry the same genes but they usually have different alleles

33
Q

What is a chromatid?

A

An identical copy of a chromosome

33
Q

Cells divide by _____ to replace the damaged cells.

A

Mitosis

34
Q

What is the name of the region where two identical chromatids are joined?

A

Centromere

35
Q

Interphase

A

Before the cell starts to divide, every DNA molecule (each chromosome) must replicate so that each new cell has a full copy of the DNA. The new molecule remains attached to the original one at the centromere.

36
Q

All offspring are _____ _______ to each other and to the parent when mitosis occurs.

A

Genetically identical

37
Q

Prophase

A

Mitosis can now begin. Each DNA molecule becomes supercoiled and compact. Each chromosome can now be seen with a light microscope and appears as two chromatids lying side by side, joined by the centromere (i.e. X-shaped)

38
Q

Metaphase

A

The nuclear membrane breaks down and the chromosomes line up along the equator (middle) of the cell.

39
Q

Anaphase

A

The centromeres split and the chromatids separate and are dragged to opposite ends of the cell.

40
Q

Telophase

A

A nuclear membrane forms around each set of chromatids (exact copies of the original chromosomes) and the cytoplasm divides.

41
Q

Give three uses of mitosis.

A

Growth, repair and asexual reproduction

41
Q

Do the homologous pairs separate in mitosis?

A

No (the chromatids separate)

42
Q

Why is DNA replicated before cell division can occur?

A

So each new cell has a full copy of the DNA

43
Q

How many cells are produced when a cell divides by mitosis?

A

Two

44
Q

Sexual reproduction creates _______ in a population.

A

Variation

45
Q

Gametes are ______

A

Haploid

46
Q

During fertilisation the nuclei of the gametes join together to form a ______.

A

Zygote

47
Q

Zygotes are _____

A

Diploid

48
Q

How many cells are produced when a cell divides by meiosis?

A

Four

48
Q

How many cell divisions are there in meiosis?

A

Two

48
Q

Are gametes haploid or diploid?

A

Haploid

48
Q

The zygote grows by simple cell division (mitosis) to form the _______.

A

Embryo

49
Q

Where in the human body does meiosis occur?

A

In the testes or ovaries

A Level Biology (11 decks)

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