DNA and Inheritance Flashcards
What is an alleles?
Alleles are different variations of the same gene
What are genotypes and phenotypes?
A genotype is the collection of alleles that determine characteristics, and can be expressed as a phenotype.
The phenotype is the visible characteristics of an organism which occur as a result of its genes.
What does homozygous represent?
Homozygous alleles are both identical for the same characteristics, for example AA or aa.
What does heterozygous represent?
Heterozygous alleles are both different for the same characteristic, for example Aa
What are genes and where are they located?
- Genes are the instructions that code our characteristics/ features.
- They are located on the chromosome (the stripe pattern) and are made of a short section of DNA.
What are chromosomes?
- Chromosomes are a collection of DNA found in the nucleolus.
- They come in pairs and we inherit half of the genes (DNA) from each parent.
How many chromosomes are in a human body cell?
There are 46 chromosomes in a standard body cell and 23 pairs of chromosomes.
What is DNA and where is it found?
- The code for proteins that writes the genetic code in our bodies that hold instructions for functions, growth and development on an organism (what to do and make)
- It is found in the genes of chromosomes and are different per individual.
What is the structure of DNA?
A double helix made of two ‘sugar phosphate back bones’ joined together by the hydrogen bonds of the base pairings.
What are the different bases in DNA and their pairings (A, T, C, G)?
- Adenine (A) ==== Thymine (T)
- Cytosine (C) ==== Guanine (G)
They are ALWAYS opposite each other
What does each base triplet (3 base pairing) code for and what does it eventually make ?
Each triplet codes for an amino acid (building blocks of a protein.
A chain of amino acids = a protein
How are the male and female sex chromosomes represented?
Male- XY
Female- XX
What are the advantages of Genetic profiling ?
- DNA evidence is reliable as it is highly unlikely that two people would share the same profile, except in the case of identical twins
- DNA profiles can be used to determine paternity (father of child)
- DNA profiles can be used to identify genetic disorders early
- DNA profiles can be used to place suspects at a crime scene
What are the disadvantages of genetic profiling?
- Stored DNA data might get into the hands of insurance, loan companies or employers who could analyse your DNA for predisposition to disease and refuse your business because of it
- Storage of DNA profiles can be seen as an invasion of privacy
- Theft of DNA profiles from a database is a real threat
- It is possible to plant DNA at a crime scene giving false evidence, or an innocent person’s DNA might be at the scene even though they had nothing to do with the crime
How is DNA prepared for genetic screening (4 steps)?
Isolation- separate DNA from other tissue
Fragmentation- use enzymes to break DNA into short lengths
Separation- pass an electric current across a layer of gel which has the DNA fragments at one end. The fragments will move across the gel. (gel electrophoresis)
Comparison- match the pattern of fragments with other samples.
