Genetics
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Genes
individual units of heredity that correspond to a particular segment of DNA, whose unique sequence (A,T,C,G) codes for a particular trait
Chromosomes
-structures made up of DNA wound around proteins called histones -one set of chromosomes from mother, one from father -22 pairs non-sex, 1 pair sex
Aneuploidy
atypical number of chromosomes
Down syndrome
trisomy 21
klinefelter’s syndrome
XXY
turner’s syndrome
X
Allele
version of the gene
Genome
-entire genetic material -1 base pair is like C-G
haploid genome
one set of chromosomes
Where is genetic information stored?
The nuclei of most of our cells in our body (not red blood cell)
Genotype
refers to the specific allele combination for a gene
Phenotype
outward expression of the genotype
Mendel’s law of segregation
A parent contains two alleles of a gene but randomly contributes just one allele of the gene to its offspring. Result: Offspring inherits the gene from mon and one from dad
Punnett square
determines potential genotypes of offspring
Homozygous dominant
ex: PP
Heterozygous
ex: Pp
Homozygous recessive
pp
Dominant allele
the one that makes a working protein
Recessive allele
one that makes a broken or no protein
Alkaptonuria (AKU)
-recessive disease -tissues accumulate black pigment -build up: homogentisic acid (HGA) -urine turns black upon oxidation
What do defects in pathways lead to?
lead to different phenotypes
Phenylketonuria (PKU) symptoms
-builds up phenylalanine -born with minimal or no symptoms, but if left untreated can lead to permanent intellectual disability -build-up damages nervous system, leading to symptoms -early treatment (low phenylalanine diet)
Genetic screen search for
-random mutagenesis in a model organism -mutants that exhibit a loss of function phenotype
How to determine gene identity of a mutant?
-complementation tests -gene mapping