Inheritance - DNA and the genome

What is DNA?

A molecule that stores/carries genetic information

Where in the cell is DNA found in prokaryotic cells? In what form is it found?

Floating in the cytoplasm; as loops - 1 large loop and several smaller loops called plasmids

Where in the cell is DNA found in eukaryotic cells? In what form is it found?

In the nucleus; as chromosomes

What is the function of DNA?

It codes for the production of proteins

How do you define a chromosome?

A long thread/strand of DNA; it is made up of thousands of genes

What is a gene?

A short section of DNA that codes for a particular sequence of amino acids, which make up a specific protein

What is a polymer?

A large molecule made up of many repeating small molecules/monomers; for a DNA molecule, the monomers are called DNA nucleotides

Describe the structure and shape of a DNA molecule

A polymer made up of 2 strands twisted around each other = a double helix

The two strands are held together by bonds between complementary base pairs

What are the complementary base pairs?

A - T

C - G

Which 4 scientists were involved in working out the structure of DNA? When did they do so?

James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins; in 1953

Which part of a DNA molecule is what is important in the production of proteins?

The sequence of DNA bases along the template strand

What are the 2 important rules about how DNA codes for the production of proteins?

1. 1 gene codes for 1 protein

2. 3 DNA bases in a row (a DNA triplet) code for 1 amino acid

Define the term 'genome'

All of the genetic material/DNA of an organism

What did the Human Genome Project involve?

It ran from 1990-2003; scientists in teams across the world sequenced the whole human genome (>3 billion base pairs) and mapped all the genes (21000) to the chromosomes on which they're found

What was the original aim of the HGP?

To find the cause of genetic diseases and to determine evolutionary relationships between species

Where were scientists able to obtain human DNA for analysis in the HGP?

Anonymous donors provided cells e.g. white blood cells; DNA obtained from nuclei

What were the advantages of the scientists being organised into teams around the world to work on the HGP?

Having many groups working on sequencing the human genome at once speeds up the process; no particular country owns the information, so information is more likely to be shared

How did scientists use genome sequencing techniques to establish a classification relationship between two species?

By sequencing the genomes of different species and comparing the DNA base sequences; if 2 species have more similar DNA sequences, they are more closely related; if 2 species have more differences in their DNA sequences, they are more distantly related

Benefits of the HGP

- understand cause of, and better treat, genetic disorders

- search for genes linked to disease

- screen embryos for genetic disorders

- trace ancient human migration patterns

- determine evolutionary relationships between species

Disadvantages of the HGP

- would you wan to know if you were more susceptible to an incurable disease?

- expensive to do sequencing (cost $3 billion)

- took 12 years to complete

- effect on life insurance

- embryo screening might lead to abortions

- designer babies

- DNA used wasn't diverse -> less info on susceptibility of different populations to difference genetic diseases

Structure of DNA in detail

Polymer made from 4 different nucleotide units each nucleotide consisting of a common sugar and phosphate and one of the 4 different bases

Long strands of DNA consist of alternating sugar and phosphate sections

DNA strands are complementary C-G, T-A