intro genetics Flashcards
histones
- proteins that chromosomes wind around
- regulates activities of genes
what are genes responsible for?
traits like eye color, heigh, enzyme function, ect.
genotype
distinct combination of genes passed down from the parents determines an offspring’s entire genetic make
true or false: the DNA sequences comprising a gene can be slightly different
true
alleles
variants of the same gene , responsible for variations in which a given trait can be expressed
why is there variation in gene expression?
due to the fact that alleles come in pairs, with one allele of each gene being inherited from each parent
true or false: all genes end up being translated into visible traits
false
phenotype
- observable traits like eye and hair color
- result of expressed genes
homozygous
two identical alleles are inherited
heterozygous
two different alleles are inherited
Dominant traits
only require one allele for the given trait to be expressed
recessive traits
can only be expressed when the genotype is homozygous
homozygous dominant
has both dominant alleles
homozygous recessive
both recessive alleles
heterozygous
one dominant and one recessive allele
incomplete dominance
occurs when one allele for a specific trait is not completely expressed over the other allele
- heterozygous alleles can display an intermediate of the dominant and recessive
NAT2*12A
present in fast acetylators but not in slow acetylators
NAT2*14B
present in slow acetylators but not in fast acetylators
intermediate acetylator phenotype’s genotype
NAT212A / NAT214B
among ethnically diverse populations; which acetylator-phenotype was identified the most frequently?
slow
what is the process of which through genetic testing determined that a particular combination of N-acetyltransfersase 2 alleles has become more frequent in Western/Central Eurasians
positive selection
why may there be positive selective advantage?
alleles for some phenotypes are more likely be passed on to subsequent generations than others
- individuals with these genotypes have a higher survival rate
- these individuals might reproduce more successfully than others in a particular environment.
selective pressure
a reason why organisms with a specific phenotype are more likely to survive
- important for natural selection, which determines which genes will be passed to subsequent generations and which will not
what was the underlying reason for the higher frequency of the slow acetylator allele?
positive selection advantage occurred when people transitioned from having a hunter-gatherer lifestyle to more of an agricultural lifestyle
- the slow acetylator phenotype was identified twice as often in populations that farmed or herded than in those that hunted and gathered. This transition caused a drastic change in people’s diets as they had to determine which plants could and couldn’t be eaten and how to use fire
lactose
Lactose, which is a disaccharide composed of galactose and glucose, is broken into its component parts by the enzyme lactase. This enzymatic reaction occurs in the small intestine of young mammals. As mammals approach adulthood, however, the gene responsible for lactase synthesis turns off. As a result, they no longer make lactase and their diets change appropriately. Presumably this is one of the main reasons why calves transition to eating grass, and dogs and cats begin to consume meat. As our human ancestors moved out of Africa and into the northern European region, they began to domesticate cows and started to consume cow’s milk and other dairy products.
1) Did lactase persist in these people? 2) Was it associated with mutations in the gene responsible for the synthesis of lactase? and 3) Does a lack of these mutations explain the condition known as ‘lactose intolerance’?
yes
what races are more lactase deficient/intolerant?
Asian, South American, and African
symptoms of lactose intolerance
abdominal pain, bloating, diarrhea and vomiting
diagnosis of lactose intolerance
genetic test to assess the makeup of the lactase gene, an intestinal biopsy to measure intestinal lactase enzyme activity, monitoring changes in blood glucose after drinking a solution containing lactose, or excluding dairy products from the diet to see if the symptoms disappear
