Exam #3 Content Flashcards
Molecular Nature of Genes
Nucleotide sequences that encode functional RNA’s (made of DNA)
- Carried on chromosomes
- Gene products (RNA and Proteins) influence phenotypic traits by regulating biochemical pathways
- Nucleotide sequence determines gene function
Gene
- Sequence of nucleotides that encodes a functional RNA
Allele
- One possible alternative forms of a gene
Many different alleles…
Can exist for a single gene
Same Alleles
- If 2 copies of a gene have identical DNA sequences
Different Alleles
- If 2 copies have 1 or more differences in DNA sequences
Locus
Where a gene is located on a chromosomes
- Same genes should be in the same location
- Different alleles of the same gene will be at the same locus
Where do new alleles come from
Mutations
- When a mutation occurs that changes the DNA sequence of a gene, a new allele is created
Haploid
Each individual only has 1 copy of each genes
- Different alleles maybe present in a population but individuals cannot have more than 1 copy of a single allele
Diploid
Each individual carry 2 copies of each gene
- Can carry at most 2 alleles
Homozygous
Both copies of gene are the same in an individual
Heterozygous
Both/two copies are different
- For any single genes: can be heterozygous for 1 gene and homo for another
Wild Type
Allele that is most common in a population
- AKA: normal, functional
- geno and pheno that are found most commonly in nature
Mutant Allele
Another allele that is not the wild type
- contains modified genetic info
- geno and pheno that differ from wild type due to an alteration in the genome
Loss of Function
Any mutation that decrease function of gene (expression, efficiency)
- there are more ways to decrease function than to increase function
Gain of Function
Any mutation that increases function of gene
- less common than loss of function
Dominance
Describes relationship between two genes
Complete Dominance
AKA: Simple dominance
Only 1 phenotype visible
- visible: dominant, not visible: recessive
- shown in mendel’s pea plants
Gene Dosage
How many copies of a gene there are
- the more copies of a gene -> the more gene products when they are expressed
Haplosufficient (more common)
In diploids many genes only require a single copy for wild type function
- 1/2 normal amount of gene product is sufficient enough for gene function
- if haplosufficient individuals carrying 1 functional allele and 1 nonfunctional allele (hetero) it will display wild type pheno
- more common bc most genes are haplosufficient
HaploINsufficient
If 1/2 normal amount of gene product is NOT sufficient for normal function
- dosage sensitive: requires more than 1 copy of function for wild type function
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Words for genes
- haplosufficient and haploinsufficient
Words for alleles
- dominant and recessive
- loss and gain of function
Loss of Function Summary
Cause by mutations that decrease gene expression or activity
- usually recessive to wild type alleles for haplosufficient
- often dominant over wildtype for haploinsufficient
- more common than gain of function