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Biology > Topic 6-Inheritance, Variation and Evolution > Flashcards

Topic 6-Inheritance, Variation and Evolution Flashcards

1
Q

What is sexual reproduction?

A

It involves the joining of male and female gametes, each containing genetic information from the mother or father

A gamete from each parent fuses to form a zygote and genetic information from each gamete is mixed so the resulting zygote is unique

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2
Q

What are gametes?

A

Sex cells (sperm and egg cells in animals, pollen and egg cells in flowering plants)

Haploid (half the number of chromosomes)

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3
Q

How many chromosomes does a normal cell have?

A

46

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4
Q

What is asexual reproduction?

A

Involves only one parent (no gametes joining)

Happens only using the process of mitosis

No genetic variation and leads to clones (genetically identical to each other and the parent)

eg bacteria, some plants and some animals

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5
Q

What must occur prior to meiosis?

A

Interphase-copies of genetic information are made during this process

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6
Q

What happens during the first stage of meiosis?

A

Chromosome pairs line up along the cell equator

The pair of chromosomes are separated and move to opposite poles of the cell (the side to which each chromosome is pulled is random, creating variation)

Chromosome number is halved

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7
Q

What happens during the second stage of meiosis?

A

Chromosomes line up along the cell equator

The chromatids are separated and move to opposite poles of the cell

Four unique haploid gametes are produced

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8
Q

Why is meiosis important for sexual reproduction?

A

It increases genetic variation

It ensures that the zygote formed at fertilisation is diploid

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9
Q

Describe fertilisation and its resulting outcome

A

Gametes join at fertilisation to produce a cell with 46 chromosomes, the normal number

This cell divides by mitosis to produce many copies

More and more cells are produced and an embryo forms

The cells begin to take on different roles after this stage (differentitation)

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10
Q

What does the term haploid mean?

A

When the nuclei only contain one set of chromosomes each

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11
Q

What does the term diploid mean?

A

When the nuclei contain two sets of chromosomes

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12
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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13
Q

What is DNA?

A

A double-stranded polymer of nucleotides, wound to form a double helix

The genetic material of the cell in found in its nucleus

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14
Q

What is each nucleotide made up of?

A

One sugar molecule, one phosphate molecule (forms backbone) and one of the four types of organic bases

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15
Q

Define genome

A

The entire genetic material of an organism

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16
Q

What are the four types of organic bases?

A

A, C, G, T

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17
Q

Why is understanding the human genome important?

A

The whole human genome has been studied and is important for the development of medicine in the future

-Searching for genes linked to different types of disease

  • Understanding and treating inherited disorders
  • Tracing human migration patterns from the past
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18
Q

What is a chromosome?

A

A long, coiled molecule of DNA that carries genetic information in the form of genes

19
Q

Define gene

A

A small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

20
Q

Describe how nucleotides interact to form a molecule of DNA

A

Sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand

Base connected to each sugar

Complementary base pairs (A pairs with T, C pairs with G) joined by weak hydrogen bonds

21
Q

Explain how a gene codes for a protein

A

A sequence of three bases in a gene forms a triplet

Each triplet codes for an amino acid

The order of amino acids determines the structure and function of protein formed

22
Q

Describe the process of meiosis

A

The cell makes copies of its chromosomes, so it has double the amount of genetic information

The cell divides into two cells, each with half the amount of chromosomes (46)

The cell divides again producing four cells, each with a quarter the amount of chromosomes (23)

These cells are called gametes and they are all genetically different from each other because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells

23
Q

Why is the ‘folding’ of amino acids important in proteins such as enzymes?

A

The folding of amino acids determines the shape of the active site which must be highly specific to the shape of its substrate

24
Q

What is protein synthesis?

A

The formation of a protein from a gene

25
What are the two stages of protein synthesis?
Transcription Translation
26
What does transcription involve?
The formation of mRNA from a DNA template
27
Outline translation
DNA double helix unwinds RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and move along the DNA strand RNA polymerase joins free RNA nucleotides to complementary bases on the coding DNA strand mRNA formation complete. mRNA detaches and leaves the nucleus
28
What is the process of protein synthesis?
The process of producing a protein from DNA
29
What are alleles?
Forms of a gene
30
Where is DNA found in a human cell?
In the chromosomes in the nucleus
31
What is a dominant allele?
It is an allele expressed even when other allele are present
32
Which bases pair up?
A T | C G
33
Strand K shows a mutation in the DNA which has caused syndrome H The enzyme IDUA helps to break down a carbohydrate in the human body The enzyme IDUA produced from Strand K will not work Explain how the mutation could cause the enzyme not to work
Mutation changes from C to T DNA code This changes the amino acid This would change the protein So it forms a different shape/changed active site The enzyme no longer fits the substrate
34
Why is DNA describes as a polymer?
They are made up of repeated units of nucleotides
35
Some parts of DNA do not code for proteins Describe how non-coding parts of DNA can affect the expression of genes
Non-coding parts can switch genes on/off
36
There are two types of cell division: mitosis and meiosis Describe three differences between the processes of mitosis
One cell division in mitosis and two cell divisions in meiosis Mitosis produces two cells but meiosis produces four daughter cells Mitosis produces genetically identical cells, but meiosis produces genetically different cells Mitosis produces diploid cells but meiosis produces haploid cells
37
Describe one similarity between the processes of mitosis and meiosis
Increase in the number of mitochondria/ribosomes/sub-cellular structures DNA replicates
38
Syndrome H is an inherited condition People with syndrome H do not produce the enzyme IDUA A mutation in the DNA causes syndrome H The enzyme IDUA helps to break down a carbohydrate in the human body The enzyme IDUA pduced from someone who has the mutation will not work Explain how the mutation could cause the enzyme not to work
Mutation causes a change the in three bases This changes the protein so it forms a different shape and changes the active site Therefore the enzyme no longer fits the substrate
39
What is an allele?
They are one form of a gene
40
What are some advantages of embryo screening?
It prevents future suffering Embryos could be used for stem cell treatment Stops baby from inheriting disease
41
What are some objections to embryo screening?
Could cause a miscarriage May lead to damage of embryo Prejudice against disabled people
42
When a cell divides by mitosis, the new cells are genetically identical What causes the cells to be genetically identical?
The DNA/chromosomes are replicated
43
Describe how embryos can be screened for the alleles that cause genetic disorders
DNA isolated from embryo Fluorescent probe is mixed with DNA Probe then binds with embryo DNA Use of UV light to show alleles/gene for disorder
44
The sequence of compounds A, C, G and T in the gene is important Explain why.
The order of three bases codes for a specific protein

Biology (8 decks)

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