Biology - DNA and inheritance Flashcards
What are gametes?
A gamete is a sex cell. In humans, gametes are sperm and eggs.
What is a gene?
A gene is a small section of DNA on a chromosome, which codes for a particular sequence of amino acids, to make a specific protein. It is the unit of heredity, and may be copied and passed on to the next generation.
What are alleles?
Alleles are different versions of the same gene. For example, the gene for eye colour has an allele for blue eye colour and an allele for brown eye colour. For any gene, a person may have the same two alleles, known as homozygous, or two different ones, known as heterozygous.
What is a genotype?
The genotype is the collection of alleles that determine characteristics and can be expressed as a phenotype.(physical characteristics)
What is a phenotype?
The phenotype is the visible characteristics of an organism which occur as a result of its genes. For example, blue eyes or brown hair.
What is a dominant allele?
A dominant allele is expressed in the heterozygote. Dominant alleles are represented by a capital letter, for example A. The allele for brown eyes is dominant. You only need one copy of this allele to have brown eyes. Two copies will also give you brown eyes.
What is a recessive allele?
A recessive allele is only expressed if the individual has two copies and does not have the dominant allele of that gene. Recessive alleles are represented by a lower-case letter, for example a. The allele for blue eyes is recessive. You need two copies of this allele to have blue eyes.
What is a homozygous allele?
Homozygous alleles are both identical for the same characteristic, for example AA or aa.
What is a heterozygous allele?
Heterozygous alleles are both different for the same characteristic, for example Aa.
What are bases in DNA?
The ‘backbone’ of each DNA strand is made from alternating sugar and phosphate molecules with paired chemicals between each strand called bases
What are the four different bases and what are their pairs?
-thymine, T
-adenine, A
-guanine, G
-cytosine, C
(T and A)
(G and C)
How do you produce a DNA fingerprint?
1) Isolation – separate the DNA from other tissues.
2) Fragmentation – use an enzyme to break the DNA into short lengths.
3) Separation – pass an electric current across a layer of gel which has the DNA fragments at one end. The fragments will move different distances across the gel. This is called gel electrophoresis.
4) Comparison – match the pattern of fragments on the gel with other samples of DNA.
What are the advantages of DNA profiling?
-DNA profiles can be used to place suspects at a crime scene
-DNA profiles can be used to identify genetic disorders early
-DNA evidence is reliable as it is highly unlikely that two people would share the same profile, except in the case of identical twins
What is genetic engineering?
Genetic engineering involves taking genes from one organism and placing them into the genome of another to modify plants to make them grow faster, bigger etc.
What are the disadvantages of DNA profiling?
-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
