Patters of Inheritance (4) Flashcards
DNA
- basic genetic material made of nucleic acid DNA
- has 4 nucleotides
- encodes info to make RNA and proteins
Genes
- unit of hereditary
- specific trait in the succesive generations of an organism ?
Alleles
- alternate forms of a gene
- responsible for a particular trait
- can be exchanged during crossing over and recombination during miosis
Locus
- location of a gene or a few genes in a chromosome
- closely located genes within a locus are less likely to be separated during recombination (meiosis)
Chromosomes
- have several loci
- ## exist as chromatin during interphase and condense into chromosomes during cell division
Genotype
- assorted collection of various genes in the chromosomes
ex.) AA, Ae, bb
Phenotype
- refers to a physical trait, condition, or biochemical aspects deterined by the genes
- ex.) eye color, sickle cell anemia
Homozygous
organism with a pair of identical alleles for a particular gene in both the homologous chromosomes
ex.) AA, aa, BB, bb
Heterozygous
- organism with mixed allele pairs for a particular gene
- an organism can be homozygous for 1 gene and heterozygous for another
- ex.) Cc, Dd
Dominant allele
allele of a gene that is expressed under both homozygous and hetrozygous conditions
- Denoted in capital letters (AA, BB, CC)
Recessive allele
allele of a gene that is only expressed under homozygous conditions
- denoted by small leters (aa, bb, cc)
Recessive allele
allele of a gene that is only expressed under homozygous conditions
- denoted by small leters (aa, bb, cc)
Law of segregation
Allele pairs separate during gamete formation and the paired condition is restored by the random fusion of gametes at fertilization
Test cross
done by hybradizing a parent with an unknown genotype with a known homozygous recessive parent to find out if the unknown genotype is homozygous or heterozygous
Law of independent assortment
the segregation of each allele pair is independent of other allele pairs. the individual allele pairs need to be located on separate loci, far from each other to allow independent assortment during gamete formation
Recombinant phenotypes
combinaiton of dominant and recessive phenotypes
Intermediate inheritance or incomplete dominance
homozygotes have a particular phenotype and heterozygotes have an intermediate phenotype showing no single gene is completely dominant.
ex.) red flowers (RR) crossed with white (rr) create all pink flowers (Rr)
Codominance
both the phenotypes are expressed at about equal levels by the expression of two types of proteins by two alleles
ex.) blood type AB showing proteins for both type A and type B in blood cells
Pleiotropy
one gene or allele codes for more than one phenotype
- several symptoms can be traced back to one gene
- individual gene affects many phenotypes
- several genes in a locus responsible for varied effects
Epistasis
- one gene interferes with the expression of another gene
- several pairs of alleles may interact to affect a single phenotype
Multiple genes
some genes exist in more than two forms
ex.) skin color in humans determined by 3 genes (A, B, C)
Sex-linked inheritance
the phenotypes affected by genes located on sex chromosomes are expressed depending on the sex of the individuals
- xx, xy
Maternal inheritance
- genes present in mitochondria and chloroplast are always inherited materanally
- only the nuclear genes are carried from on from one gamete to another by the male
Environmental effect on gene expression
the interaction of the environment on one gene expression results in wider variation especially in genes controlled by multiple genes
ex.) sunlight can intensify melanin pigmentation
