3.1 Flashcards
What is a gene
A heritable factor that consists of a length of DNA which codes for a polypeptide chain
What is a locus?
the specific location of a gene on a chromosome
What is an allele?
a specific form of a gene (alternate alleles differ from each other by one or a few base pairs)
What is a mutation?
a change in the base sequence of DNA
what is a genome?
all the genetic information in a cell or organism
how many alleles of each gene do most cells contain? why?
we have 2 copies of each chromosome
therefore we have 2 copies of each gene and thus 2 alleles of each gene (can be the same or different)
what can you say about the loci of alleles of a gene?
the 2 copies of each gene (& therefore the 2 alleles) have the same loci on homologous chromosomes
Comparison of the number of genes in humans with other species
Homo sapiens: have 23000 genes
Escherichia coli: have 3200 genes
Populus trichocarpa: have 46000 gene
number of genes does not correlate to complexity of an organism
prokaryote will have low number of genes
plants will have high number of genes
What is meant by “linked genes”
linked genes are genes which are present on the same chromosome
-they have a much higher likelihood to be inherited together
-the closer together their loci, the higher the probability
What are the positions in a gene where different bases may be present called?
Single Nucleotide Polymorphisms (SNPs)
What are factors that can cause mutations?
Radiation: UV, x-rays, gamma-rays
Chemicals: asbestos, cigarette smoke
Viruses: HPV
What are the consequences of gene mutations?
—> a change to one triplet in DNA
—> changes one codon in mRNA
—> changes one amino acid in a polypeptide chains—which changes a proteins structure and function
MOST MUTATIONS ARE HARMFUL, SOME ARE NEUTRAL, RARELY CAN THEY BE BENEFICIAL (determined by natural selection
The human genome project
they sequenced the complete human genome
found that humans have approximately 20-25000
consist of roughly 3 billion base pairs
80% of genome is used to control biological functions
DNA sequences b/w humans is 99.5% identical
