Biology 6: Inheritance, Variation And Evolution

Front 1

Define gamete

Back 1

Sex/reproductive cell with half chromosomes (23 in humans) eg ova and sperm

Front 2

Define chromosome

Back 2

A part of DNA - there are 46 in a human body cell, half from each parent

Front 3

Define gene

Back 3

A section of DNA which codes for a specific characteristic

Front 4

Define allele

Back 4

Different versions of a gene (T Vs t)

Front 5

Define dominant

Back 5

A dominant allele is one that will always present, even if only one copy is present (Tt or TT)

Front 6

Define recessive

Back 6

A recessive allele will only present if both copies are there (tt)

Front 7

Define homozygous

Back 7

Both alleles are the same (TT or tt)

Front 8

Define heterozygous

Back 8

One of each allele (TT)

Front 9

Define genotype

Back 9

A pair of alleles eg Tt

Front 10

Define phenotype

Back 10

How a genotype presents eg brown eyes

Front 11

Examples of single gene controlled phenotype

Back 11

Fur colour in mice, red/green colour blindness

Front 12

What are most phenotypes made from

Back 12

More than one genotype

Front 13

What sort of allele is Polydactyly caused by

Back 13

Dominant (HH or Hh)

Front 14

What sort of allele causes cystic fibrosis

Back 14

Recessive (ff)

Front 15

How many chromosomes do human body cells have

Back 15

23 pairs (46)

Front 16

Which pair of chromosomes determine sex

Back 16

Pair 23

Front 17

Chromosome pair for female sex organs

Back 17

XX

Front 18

Chromosome pair for male sex organs

Back 18

XY

Front 19

What is asexual reproduction?

Back 19

It involves only one parent and no fusion of gametes. The offspring are genetic clones of the parent. Only mitosis is involved.

Front 20

What happens during sexual reproduction?

Back 20

There is a mixing of genetic information from two parent organisms. A male and a female gamete fuse to form a new, genetically individual cell, which divides to form a new organism. The production of gametes involves meiosis.

Front 21

What is the process of meiosis?

Back 21

A cell copies its genetic information and splits into two new cells.

In these cells, the DNA is shuffled about to form new chromosomes.

Then, these cells split without copying the DNA. This forms four haploid gametes.

Front 22

What happens during and after fertilisation?

Back 22

Two gametes join to form a zygote, which has the normal number of chromosomes. The zygote then divides by mitosis to form an embryo, and then a new organism.

Front 23

What are the advantages of sexual reproduction?

Back 23

Produces variation in offspring

Variation gives a survival advantage by natural selection.

Natural selection can be sped up by selective breeding.

Front 24

What are the advantages of asexual reproduction?

Back 24

Only one parent needed - no need to find a mate

More time and energy efficient

Faster than sexual reproduction

Many offspring can be produced

Front 25

Some organisms reproduce both sexually and asexually. What are some examples?

Back 25

Malaria reproduces in the human host, and sexually in the mosquito

Strawberries produce seeds sexually, but also runners asexually

Fungi produce asexually with spores, but also sexually to produce variation.

Front 26

What is the structure of a DNA molecule?

Back 26

It is a double helix shaped polymer with a sugar-phosphate backbone linked by base pairs of four different nucleotides.

Front 27

What is a gene?

Back 27

It is a small section of DNA that codes for a particular sequence of amino acids that will make a protein.

Front 28

What is a genome?

Back 28

The entire genetic sequence for an organism.

Front 29

Why is it important that we understand the human genome?

Back 29

We can search for the causes for genetic diseases

We can understand and possibly treat such diseases

We can trace human migration patterns from the past.

Front 30

What are the four nucleotide bases, and what pairs do they come in?

Back 30

A and T

C and G

Front 31

What does a sequence of three bases code for?

Back 31

An amino acid. The order of these triplets determines the protein that is made.

Front 32

What is protein synthesis?

Back 32

The process of making proteins: a piece of RNA copies a section of DNA, and attaches itself to a ribosome (the site of protein synthesis). Some more RNA brings the appropriate amino acids, and the ribosome reads the RNA and assembles the amino acids in the correct order.

The protein is then curled into the right shape.

Front 33

How do variations in DNA influence phenotype?

Back 33

In coding DNA, it might code for a slightly different protein.

In non-coding DNA, it might influence which gene gets expressed.

Front 34

What is selective breeding, or artificial selection?

Back 34

The process by which humans breed plants and animals for particular characteristics.

This is done by choosing a male and a female member of the species who exhibit the desired trait, breeding them together, and then choosing the best offspring to breed again. Eventually, all offspring will exhibit the desired trait.

Front 35

Examples of desired characteristics.

Back 35

Disease resistance in food crops

Animals which produce more meat or milk

Domestic dogs which are gentle and obedient

Large, brightly coloured, unusual or well scented flowers.

Front 36

What is the downside of selective breeding?

Back 36

It can lead to inbreeding, where some breeds have genetic defects due to a narrow gene pool, or are particularly prone to disease. Some plant species can become infertile.

Front 37

Describe genetic engineering.

Back 37

A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.

Front 38

What is an example of how plants have been engineered?

Back 38

They have been engineered to be resistant to disease, herbicides, to produce insecticides, to produce larger fruit, and to be more nutritious (golden rice).

Front 39

What is an example of how bacteria have been engineered?

Back 39

They have been engineered to produce useful substances, such as human insulin.

Front 40

What concerns do people have about genetic engineering crops?

Back 40

May have a negative effect on wild flower and insect populations. May cross pollinate with weeds creating 'super-weeds'. Some people feel the effect on human health of eating GM crops has not been explored enough (yuck-factor).

Front 41

What area of medicine might GM be useful for in the future?

Back 41

Medical researchers are looking at the possibility of genetic modification to overcome inherited disorders.

Front 42

What are the main steps of genetic engineering?

Back 42

An enzyme isolates the required gene

The gene is inserted into a vector (plasmid)

The vector is used to insert the gene into the required cells

Cells are transferred to the organism at an early stage of development so the traits can develop.

Front 43

What is tissue culture?

Back 43

Using small groups of cells from plant to grow identical now plants (clones).

This is used to preserve dying species, and commercially.

Front 44

What are cuttings?

Back 44

A stem is cut from a parent plant, dipped in rooting powder and planted. It becomes a new plant.

Many clones can be produced this way quickly in one's back garden.

Front 45

What is an embryo transplant?

Back 45

When an embryo with desired characteristics is at the eight cell stage, it is split into four, two cell embryos which are each implanted into a different surrogate mother. The offspring are all identical.

This process is also called twining.

Front 46

What is the process of adult cell cloning?

Back 46

Nucleus removed from an ova

Nucleus removed from a body cell, and put into the empty ova.

Ova with new nucleus given an electric shock to stimulate mitosis.

Once the ova has formed an embryo, it is inserted into a surrogate mother.

The baby will be a clone of an adult animal.