Topic 6 - Inheritance, Variation and Evolution Flashcards

1
Q

Compare sexual and asexual reproduction.

A

Sexual reproduction:

  • – The fusion of male and female gametes.
  • – Egg and sperm in animals
  • – Egg and pollen in flowering plants
  • – Two parents so there is a mix of genetic information which leads to variety in the offspring.
  • – Involves meiosis

Asexual reproduction:

  • – One parent
  • – No fusion of gametes
  • – Produces genetically identical offspring (clones)
  • – Involves mitosis
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2
Q

What is the process of meiosis?

A
  • – Genetic information is duplicated and then chromosomes arrange themselves in pairs
  • – In the first division, chromosomes line up in the centre of the cell
  • – Pairs are pulled apart and each new cell has one copy of each chromosome
  • – In the second division, chromosomes line up in the centre of the cell again and the arms of the chromosomes are pulled apart by cell fibres
  • – Four gametes are produced each with a single set of chromosomes
  • – Gametes are all genetically different from each other
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3
Q

What happens after meiosis?

A
  • – Gametes fuse during fertilisation to restore the normal number of chromosomes in a cell (46)
  • – The new cell divides by mitosis to replicate itself
  • – Mitosis repeats many times to produce lots of many cells in the embryo
  • – As the embryo develops, cells differentiate into different specialised cells
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4
Q

What are the advantages and disadvantages of sexual and asexual reproduction?

A

Sexual reproduction:

  • – Variation in offspring
  • – If there is a change in environment, the variation increases the survival of the species. This is a survival advantage.
  • – More likely to breed successfully and pass the genes for the characteristics on. This is natural selection.
  • – Natural selection can be sped up by humans in selective breeding to increase food production.

Asexual reproduction:

  • – Requires one parent
  • – Less time and energy are used as organisms don’t have to find a mate
  • – Faster than sexual reproduction
  • – Identical offspring can be produced under favourable conditions
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5
Q

Give three organisms that can reproduce both asexually and sexually.

A

Malarial parasites:
— Asexually in the human host but sexually in the mosquito.

Fungi:

  • – Species of fungus release spores.
  • – Asexually-produced spores produce fungi that are genetically identical and sexually-produced spores introduce variation often in response to unfavourable conditions which increase the chance of survival

Plants:
— Seeds can be produced sexually but asexually by runners such as strawberry plants or bulb division such as daffodils.

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6
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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7
Q

What is the structure of DNA?

A
  • – Polymer made up of repeating units of nucleotides
  • – Two strands coiled together to form a double helix structure.
  • – Four different bases: A, C, G, T
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8
Q

What is a gene?

A

Gene:

  • – A small section of DNA
  • – Each gene codes for a particular sequence of amino acids to make a specific protein.
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9
Q

Define a genome. What is the importance of learning the entire genome?

A

Genome:
— Entire genetic material of an organism

Importance of learning:

  • – Scientists can identify genes linked to diseases
  • – Can identify genes linked to inherited disorders which helps to understand them better and develop an effective treatment
  • – Can trace human migration patterns from the past
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10
Q

What does each nucleotide consist of?

A

A phosphate (oval), a sugar (pentagon) and a base (rectangle)

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11
Q

What are the complementary base pairings?

A
  • – A pairs up with T

- – C pairs up with G

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12
Q

How many bases code for a specific amino acid?

A

3 bases

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13
Q

What is the role of mRNA? Also, what are the complementary pairs between DNA and mRNA?

A

mRNA acts as a messenger to get the code from the DNA to the ribosome to make protein.

A links to U
T links to A
C links to G
G links to C

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14
Q

What happens after a chain of amino acids has been assembled?

A

The chain folds into a unique shape to allow the protein to perform its task such as enzymes, keratin, hormones etc.

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15
Q

What are the three different types of mutations?

A

Insertion:

  • – A new base is inserted into the DNA base where it shouldn’t be
  • – Changes the way the base is ‘read’
  • – Has knock-on effect on bases further down the sequence

Deletion:

  • – A new base is deleted from the DNA base
  • – Changes the way the base is ‘read’
  • – Has knock-on effect on bases further down the sequence

Substitution:
— A random base is changed to another base in the sequence

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16
Q

Explain the terms:

  • – allele
  • – dominant/recessive
  • – homozygous/heterozygous
  • – genotype/phenotype
A

Allele:
— A version of a gene

Dominant/Recessive:
— A dominant allele is always expressed if only one allele is present. It is shown with a capital letter. A recessive allele is only expressed if both copies are present. This is shown with a lowercase letter.

Homozygous/Heterozygous:
— Homozygous is when two alleles present are the same. Heterozygous is when two alleles present are different.

Genotype/Phenotype:
— Genotype is the combination of alleles present. Phenotype is the characteristic.

17
Q

What are two examples of inherited disorders?

A

Cystic fibrosis:

  • – Caused by a recessive allele
  • – Thick mucus builds up in air passages or pancreas

Polydactyl:

  • – Caused by dominant allele
  • – Person is born with extra fingers or toes
18
Q

What are the reasons for and against embryonic screening?

A

For:

  • – Stop people suffering
  • – Having to treat disorders costs a lot of money.
  • – There are laws in place to stop people from taking it too far such as selecting the gender of their babies

Against:

  • – Increased prejudice as it is as though people with genetic disorders are ‘undesirable’
  • – People could start taking it too far to pick the most ‘desirable’ embryo
  • – Expensive
19
Q

How do sex chromosome combinations determine sex?

A

Male: XY
Female: XX