2.3 - DNA & inheritance

What is DNA made of?

2 strands made of sugar and phosphates; a sugar phosphate backbone

What are the 2 strands of DNA joined by?

Bases, held together with hydrogen bonds

What are the complimentary base pairs in DNA?

• Adenine and thymine

• Cytosine and guanine

What is a triplet code, and what does it do?

1. A sequence of 3 bases in a gene form a triplet

2. Each triplet codes for an amino acid

3. The order of amino acid chains determines the structure and function of the protein formed

Give 4 purposes of DNA PROFILING

1. Identifying criminals

2. Paternity testing

3. Classification

4. Detecting genes associated with a particular disease

Negatives of DNA profiling

Privacy/ownership issues - people may object to their DNA being retained by police

How is DNA profiling carried out?

1. Cut DNA into short pieces

2. Separated into bands

What is the Human Genome Project?

Successfully mapped the position of all the genes on each human chromosome

(Human genome - all the genetic information in a human)

Why is the Human Genome Project important?

Important for medicine-

New ways to treat/cure/prevent disease

Define: gene

Gene: a section of DNA that codes for a specific trait

Define: allele

Allele: a different version of the same gene

(E.g. eye colour gene: brown, blue, green)

Define: genotype

Genotype: the genetic makeup

Define: phenotype

The characteristic that is shown because of your genotype

Define: homozygous

Both alleles are the same

Homozygous DOMINANT: NN

Homozygous RECESSIVE: nn

Define: heterosexual

Both alleles are different

E.g. Nn

The dominant allele will be … in the phenotype when it is present

The dominant allele will always show in the phenotype when present

DO NOT SAY “IT IS STRONGER”

A recessive allele will be … when a dominant allele is present in a heterozygote

A recessive allele will be “hidden” when a dominant allele is present in a heterozygote

What chromosomes can an egg cell have?

Egg cells ONLY have X chromosomes

What chromosomes can a sperm cell have?

Sperm cells can have X OR Y chromosomes

What chromosomes do females have?

XX

What chromosomes do males have?

XY

Which set of chromosomes decides the sex?

The 23rd set of chromosomes are the sex cells.

Which sex cell determines the gender of a baby?

Sperm

(Egg cells are only XX , sperm is XY)

Define: F1

First generation in a genetic cross - the offspring produced when 2 organisms from the F1 generation are bred together

Define: F2

Second generation in a genetic cross - the offspring produced when 2 organisms from the F1 generation are bred together

Define: selfing

An artificial methods of self-pollinating plants

What is genetic engineering/modification?

Transferring a gene from one organism to another

What are 4 advantages of genetic engineering?

1. Increased crop yields

2. Useful in medicine

3. GM crops produce scarce resources

4. GM crops can be used as biofuels as an alternative to fossil fuels

What are 4 disadvantages of genetic engineering?

1. Long-term consumption of GM crops are unknown

2. Negative environmental impacts - reduction in biodiversity, impact on food chain

3. Are expensive and LEDCs may become dependent on businesses that sell them

4. GM plants could become a pest themselves