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CB3 Flashcards

1
Q

What is the name of a fertilized egg cell?

A

A zygote.

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2
Q

How is a zygote formed?

A

When two gametes fuse during fertilization. The zygote then forms a ball of cells using a type of cell division called mitosis.

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3
Q

What is a gamete?

A

A sex cell.

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4
Q

What is a genome?

A

The DNA of an organism.

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5
Q

Where is the human genome found?

A

On 46 very long molecules of DNA, and each molecule is inside a chromosome.

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6
Q

What are genes?

A

Sections of a DNA molecule that each contain a code for making protein.

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7
Q

What is meant by ‘A Polymer’?

A

They are proteins that are made by linking different amino acids together in a chain. The order of amino acids is controlled by a gene.

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8
Q

How many chromosomes does the human body contain?

A

It contains two sets of 23 chromosomes (46 chromosomes in total)

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9
Q

What process of cell division is used for gametes?

A

Meiosis.

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10
Q

How are gametes produced?

A
  1. Each chromosome replicates. The two copies remain attached, making each chromosome look like an X.
  2. The two sets of chromosomes ‘pair up’, forming 23 pairs, and the pairs then separate into two new cells.
  3. Next, the two copies of a chromosome in each X-shape split into two more new cells. Meiosis therefore produces four haploid daughter cells, which is how gametes are produced.
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11
Q

What is the difference between Mitosis and Meiosis?

A

The process of Cytokinesis occurs twice in Meiosis but only once in Mitosis, so there ends up being 4 daughter cells instead of 2.

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12
Q

Where is DNA located?

A

In the nucleus.

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13
Q

What are chromosomes?

A

Tightly coiled DNA that is packaged up with proteins.

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14
Q

Describe DNA’s shape?

A

Two strands, joined together by pairs of substances called bases to form a double helix shape.

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15
Q

What are the four bases of DNA

A
  1. Adenine
  2. Thymine
  3. Cytosine
  4. Guanine
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16
Q

What are complementary base pairs?

A

Two DNA bases that fit into each other and link by weak hydrogen bonds.

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17
Q

What are the two complementary base pairs?

A
  1. A and T (Adenine and Thymine)
  2. C and G (Cytosine and Guanine)
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18
Q

What is each DNA base attached to?

A

They are attached to a sugar and each sugar is attached to a phosphate group. The sugars and phosphate groups form the backbone of DNA strands.

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19
Q

Is DNA a Polymer?

A

DNA is made of many similar units joined in a chain, and so it is a polymer.

20
Q

What is a hydrogen bond?

A

A slightly negatively charged part of one base that attracts a slightly positively charged part of another base forms a hydrogen bond.

21
Q

How many hydrogen bonds do Cytosine and Guanine form between them?

A

Three hydrogen bonds.

22
Q

How many hydrogen bonds do Adenine and Thymine form between them?

A

Two hydrogen bonds.

23
Q

Why does Cytosine only pair with Guanine and Adenine only pair with Thymine?

A

As each DNA pair form different amounts of hydrogen bonds between them.

24
Q

How can DNA be used for identification?

A

Scientists can use the order of DNA to identify skeletons by comparing the DNA code of the skeleton’s bones to that of living relatives of who they suspect the skeleton to be.

25
What is an allele?
Different forms of the same gene.
26
What is genetic variation?
Differences between organisms caused by differences in the alleles they inherit from their parents, or differences in genes caused by mutation.
27
How does the idea of alleles help to explain why we all look different?
Since there are two copies of every chromosome in a body cell nucleus, a body cell contains two copies of every gene. Each copy of a gene may be a different allele, and because all of them have different combinations of alleles in each person, each person has slightly different characteristics.
28
Define 'Homozygous'?
When both alleles for one gene are the same (e.g. RR alleles are Homozygous)
29
Define 'Heterozygous'?
When the alleles for one gene are different (e.g. Rr alleles are Heterozygous)
30
What characteristics would a flower inherit from two 'Rr' flowers in genotype? (R=Purple colour, r=White colour)
25%=RR (Homozygous dominant) 50%=Rr (Heterozygous) 25%=rr (Homozygous recessive)
31
Define 'Genotype'?
The alleles for a certain characteristic that are found in an organism (e.g. RR,Rr,rr)
32
Define 'Phenotype'?
The characteristics produced by a certain allele (e.g. Purple colour, Green eyes)
33
What are the two types of Sex Chromosomes and which do each gender have?
X and Y (Females have XX and Males have XY)
34
How do Punnet squares tell us if someone has inherited a disorder, who is a carrier and who doesn't have it whatsoever?
Two recessive alleles=Have the disorder One dominant and one recessive allele=A carrier of the disorder Two dominant alleles=Doesn't have the disorder and is not a carrier
35
What is a family pedigree chart?
A chart to show how genotypes and their resulting phenotypes are inherited in families.
36
What is Melanin?
A protein that makes hair, eyes and skin darker in colour.
37
What is a Mutation?
A change in a gene that creates a new allele. These often occur during cell division.
38
When do Mutations happen?
When there is a mistake in copying DNA during cell division.
39
How can the Human Genome Project (mapping peoples genome) be useful?
1. It can indicate their risk of developing diseases that are caused by different alleles of genes. 2. It can identify which medicines might be best to treat a persons illness, because the alleles we have can affect how medicines work in the body.
40
What is environmental variation?
Differences between organisms caused by environmental factors such as the amount of heat, light and damage by other organisms.
41
What are acquired characteristics?
Characteristics that are changed by the environment during the life of the individual.
42
What two groups can variation be grouped into?
1. Discontinuous variation 2. Continuous variation
43
What is 'Discontinuous variation'?
Where the data can only take a limited set of values, they can't be measured by exact measurements (e.g Gender, Blood type, Eye colour)
44
What is 'Continuous variation'?
Where the data can be any value in a range (e.g. Height, Weight, Skin colour)
45
What pattern does continuous variation often fall under?
It often forms a bell shaped curve, known as a normal distribution.
46
What is normal distribution?
1. When the most common value is the middle value in the whole range 2. The further a value is from the median, the fewer individuals have that value

Biology (9 decks)

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