4.1.1

What are eukaryotic chromosomes made up?

DNA and proteins

4.1.2

What is a gene, allele and genome?

Gene: a heritable factor that controls a specific characteristic

Allele: an alternative form of a gene

Genome: the complete genetic material of an organism

4.1.3

What is a gene mutation?

This is a permanent change in the sequence of base pairs in the DNA

4.1.4

What is the consequence of a base substitution mutation with reference to sickle cell anaemia?

Only one base needs to be different to cause significant damage.

In sickle cell anaemia the base sequence GAG is replaced with GTG.  This means that during translation the wrong amino acid is added to the sequence creating a completely different protein.  This results in the red blood cells having a sickle shape.

4.2.1

What is meiosis?

A reduction division of a diploid nucleus to form four haploid cells

4.2.2

What are Homologous chromosomes?

A pair of chromosomes with genes for the same characteristics on them.  One is from the mother and the other is from the father.

4.2.3

What happens during Meiosis 1?

In prophase 1, the chromosomes have replicated themselves and they pair up within the cell as the cell membrane and nucleolus breaks down.

In Metaphase 1 each pair of chromosomes lines up on the equator of the cell.  Crossing over of genes occurs here.

In Anaphase, one of each pair of chromosomes moves to each pole.

In Telophase 1 the cell membrane starts to pinch together but before this process finishes completely Meiosis 2 begins.

4.2.3

What happens during Meiosis 2?

Meiosis 2 starts immediately after Meiosis 1 and there is no further replication of chromosomes.

Meisis 2 occurs just as mitosis occurs but the result is 4 haploid cells.

4.2.4

What causes down's syndrome?

Non-disjunction can lead to down's syndrome.  This is when during Meiosis, both chromosome 21s go in the same direction instead of being split up.  This means that when the egg is fertilised, the individual ends up with 3 chromosome 21s.

4.2.5

What is karyotyping?

4.2.6

How is karyotyping performed?

Using cells collected from chorionic villus sampling or amniocentesis for pre-natal diagnosis of chromosome abnormalities

4.3.1

What is Genotype and Phenotype?

4.3.1

What is a dominant, recessive and codominant allele?

Dominant alleles are always expressed.

Recessive alleles are only expressed in the homozygous condition.

Codominant alleles are both expressed at the same time in the heterozygous condition

4.3.1

What does homozygous and heterozygous mean?

4.3.1

What is the locus of a gene?

The position on the chromosome where a particular gene is found

4.3.1

What is a carrier in terms of genetics?

An individual who is heterozygous for a recessive genetic condition such as colourblindness.  The individual doesn't actually have the disease but does have the ability to pass it on.

4.3.1

What is a test cross?

An experimental cross with an individual whose genotype is unknown with an individual who is homozygous recessive for the condition to determine whether the first individual is homozygous or heterozygous.

4.3.4

What are blood types examples of?

Codominance and multiple alleles.

4 blood types

A - I^AI^A /I^Ai

B - I^BI^B/I^Bi

AB - I^AI^B

O - ii

4.3.7

What is sex linkage?

This is when the gene for a characteristic is located on the X chromosome.

4.4.1

What is the purpose of a PCR?

4.4.2

What is gel electrophoresis?

When fragments of DNA cut by restriction enzymes in specific areas move in an electric field according to their size and charge.

4.4.3

When is gel electrophoresis used?

In DNA profiling for criminal investigations

Determining paternity

4.4.6

What are 3 outcomes of sequencing the entire human genome?

Genetic diseases can be better understood

genetic screening can be used to see if an individual is suceptible to a particular disease.

Research into disease can be focused only on the genes involved.

4.4.7

What does it mean that 'the genetic code is universal'?

When DNA is transferred between species the amino acid sequence of polypeptides translated remains the same

4.4.8

What is a basic technique for gene transfer?

Plasmids are used in a bacterium.

Restriction enzymes are used to cut the gene required out of the DNA.

The same restriction enzymes are then used on the plasmid so that the ends will match up (sticky ends)

The required gene is mixed with the plasmid and DNA Ligase joins them together

4.4.9

What are two uses of genetically modified crops?

BT Corn

Golden rice

4.4.10

What are the benefits of BT corn?

less crops will die

There is a higher yield of crops

a smaller amount of land can be used to grow the same amount of crops so that the extra land can be used for conservation purposes.

farmers will make more money

4.4.10

What are possible harmful effects of BT corn?

The corn may cross pollinate with plants in the wild so that other plants have the BT toxin in.  This could kill other wildlife.

The BT toxin could have possible effects on humans.

4.4.11

What is a clone?

A group of genetically identical organisms or copies of a cell all derived from the same parent cell