Chapter 5: Genetics Flashcards
signs a pedgree is autosomal dominant
2 affected parents can have an unaffected offspring, parents must be heterozygous
signs a pedgree is autosomal recessive
2 unaffected parents can have an affected offspring, parents must be heterozygous
signs a pedgree is X-linked dominant
100% incidence of affected daughters from an affected father suggests it
signs a pedgree is X-linked recessive
100% incidence of affected sons from an affected mother suggests it
what are multiple alleles
for most traits, there are more than two alleles for a gene. produces discontinous variation, e.g. groups not a range.
what is polygenic inheritance.
the inheritance of more than one gene that affect the inheritance of a single characteristics, gives continuous variation
what causes continuous variation
genetic and environmental factors
what causes discontinuous variation
genetic factors
what is complete dominance
one allele in a pair shows complete dominance over the other.
what is incomplete dominance
there is an intermediate phenotype, neither allele is completely dominant, one allele for a specific trait is not completely expressed over its paired allele.
what is codominance
both alleles are completely, independently and equally expressed. both alleles in the genotype are observed in the phenotype.
gene definition
A gene is a section of DNA whose base sequence codes for a specific protein.
homologous
(of chromosomes) pairing at meiosis and having the same structural features and pattern of genes.
homozygous
having two identical alleles of a particular gene or genes.
chromosome definition
A chromosome is a single molecule of DNA that is wrapped around proteins. Most human cells have 46 chromosomes.
DNA in prokaryotes
relatively small amount of DNA
DNA is unbound
have a single, circular chromosomes
Chromosomes reside in the cytoplasm
DNA in eukaryotes
Relatively large amount of DNA
DNA is bound (wrapped around histones)
forms linear chromosomes
chromosomes reside in the nucleus
define DNA
a type of nucleic acid that is responsible for storing genetic information in cells
what does DNA do ?
acts as an instruction manual, contains information needed for growth, survival and reproduction
