Chapter 15 - Evidence For Evolution Flashcards
How are genes gained or lost?
New genes are gained by mutation.
Other genes are lost by natural selection, random genetic drift etc.
Species that are more distantly related have…
More differences in their DNA, where as species that are more closely related share a greater portion of DNA.
Define genome
The complete set of genetic material within a cell ; an organisms complete set of DNA.
How much of a DNA difference is there between humans, chimpanzees, gorillas and orang-utans.
Human and chimpanzee = share 98.8%, thus 1.2% difference
Human and gorilla = share 98.4%, thus have a 1.6% difference
Human and organ-utan = share 97.6%, thus have a 2.4% difference
What is the difference between human chromosomes and chimpanzee chromosomes?
Chimpanzees have 24 pairs of chromosomes while humans have 23. It is believed that two small chromosomes in chimpanzees happened to fuse together in humans at some time in the past.
Define junk DNA.
Non-coding sequences of nucleotides in DNA. They have no apparent function and appear to serve no purpose.
What does ERV stand for and what is it?
ERV are endogenous retroviruses which are viral sequences that have become part of an organisms genome. They are also referred to stretches of non - functional DNA.
Explain the process of ERVS entering cells.
Retroviruses store their genetic information as RNA not DNA.
Upon entering a cell, a retrovirus copies it’s RNA into DNA (a process called reverse transcription).
The DNA then becomes endogenous if it inserts into germinal cells/ gametes.
The offspring of the infected individual will then have a copy of the ERV at the same location, in the same chromosome, in every single one of their cells.
ERVS make up 8% of the human genome.
What is mitochondrial DNA? And how many are there?
Mitochondrial DNA are small, circular molecules of DNA found in the mitochondria of a cell. There are about five to ten of these molecules in each mitochondrion.
Most cells contain large numbers of mitochondria and usually gave between 500-1000 copies of the mtDNA molecule. In humans, the mt DNA genome consists of about 16500 base pairs.
How many genes are in mtDNA?
MtDNA has 37 genes.
24 - containing the code for making transfer RNA molecules.
13 - have instructions for making enzymes necessary for cellular respiration.
How is mitochondrial DNA passed on?
Mitochondrial DNA is passed on by maternal ancestors, as male mtDNA are destroyed after entering the cell.
We inherit nuclear DNA from our parents but we inherit mitochondrial DNA only from our mothers.
What are two ways mtDNA has contributed to understanding evolution?
- scientists can compare the mtDNA of any two individuals to provide an estimate of the closeness of their relationship through their maternal ancestors.
- scientists are able to trace migration routes of ancient people.
How many kinds of amino acids are there?
20 kinds of amino acids.
How can protein sequences be used to understand evolution?
- Animals of the same species have the same amino acid sequences in their proteins.
- Animals of different species have different amino acids or they are arranged in a different order.
- The longer the period of time involved, the greater the number of amino acids that are different.
List the 20 different amino acids and their single letter codes.
Alanine A Arginine R Asparagine N Asparagine D Aspartic acid D Cysteine C Glutamic acid E Glutamine Q Glycine G Histidine H Isoleucine I
Leucine L Lysine K Methionine M Phenylalanine F Proline P Serine S Threonine T Tryptophan W Tyrosine Y Valine V
