Biology 6.2 Flashcards
(25 cards)
Gene
Unit of information containing a specific trait that is passed from parent to offspring, encoded on specific location on a chromosome referred to as the locus
Allele
Variation of a gene, can arise from mutation. Each human has 2 alleles of each gene; one of maternal and one of paternal origin. Dominant allele can mask a recessive allele or be co-expressed with another dominant allele.
- homozygous chromosomes: 2 identical alleles at locus “AA” or “aa”
- heterozygous chromosomes: 2 different alleles at a locus “Aa”
Genotype
Particular alleles of a gene
Phenotype
Observable traits as a result of genotype
P, F1, F2
P = Parental generation F1 = First generation offspring F2 = Second generation offspring
Law of segregation
When forming gametes, homologous chromosomes are separated ensuring each gamete gets only one allele of each gene
Law of independent assortment
Homologous chromosomes go to separate gametes independent of maternal or paternal origin
Test cross or Punnett square
Determine genotype of unknown organism by crossing it with homozygous recessive “aa” genotype, can see if unknown organism is homozygous dominant or heterozygous
Types of genetics dominance
Complete dominance, incomplete dominance, codominance
Complete dominance
A type of genetics dominance. Dominant allele masks recessive allele entirely
Incomplete dominance
A type of genetics dominance. Phenotypes of dominant and recessive allele are blended and both partially expressed, like a mix (ex. white and red to make pink)
Codominance
A type of genetics dominance. Both phenotypes completely expressed, no blending (ex. patches).
Blood group genetics
In humans, gene that encodes enzyme that indicates structure of a glycolipid on blood cells is responsible for ABO blood types. Alleles are:
- I^A: encodes for glycolipid A on RBC, dominant allele
- I^B: encodes for glycolipid B on RBC, dominant allele
- i: encodes no glycolipids on RBC, recessive allele
Body has immune response against unknown glycolipids in the body
Type A blood
I^AI^A or I^Ai, glycolipid A
Type B blood
I^BI^B or I^Bi, glycolipid B
Type AB blood
I^AI^B, both glycolipid A and B, universal recipient, co-dominant
Type O blood
ii, neither glycolipid A nor B, universal donor
Pleiotropy
When 1 gene has multiple phenotypes
Epistasis
One gene affects expression of different gene
Polygenic inheritance
Many genes acting together to makes a single phenotype, produces a continuous variation in phenotype (ex. skin colour, height)
Nondisjunction
In gametogenesis, chromosomes may fail to separate properly in either anaphase I or anaphase II, causing gametes to have either extra or missing chromosomes called aneuploidy
Chromosomal abberations
Caused by improper DNA replication or mutagenic agents in somatic of germ cells
- Duplications: segment of chromosomes is repeated
- Inversions: segment of chromosomes is taken out, flipped, put back
- Translocations: one segment of chromosome moves to another chromosome
Linked genes
Genes occupying very close regions of the same chromosome, usually inherited together, less likely separated during crossing over in gametogenesis, close loci
Sex-linked inheritance
Genes on sex chromosomes that are inherited based on sex, usually on X but can also be on Y
