Ch. 9 Patterns of Inheritance Flashcards
Genetics
Science of heredity (study of the inheritance of traits)
- founded by Gregor Mendel
Who was Gregor Mendel?
“Father of Genetics”
- experiment with pea plants for seed shape, color (flower/seed), pod shape, flower position, stem length plant mating
- parents pass onto offspring discrete heritable factors that retain individuality generation to generation
Chromosome Theory of Inheritance
Genes are physical units located on chromosome and the behavior of chromosomes during meiosis/fertilization determine inheritance patterns
Mono-hybrid cross
Cross w/ only 1 variable at a time
Allele
Alternative form of a gene
- each trait is determined by 2 alleles (1 from each parent)
Dominant
Allele that rules/dominates over other
- expressed (A)
Recessive
Hidden/masked by dominant allele
- expressed w/ 2 recessive alleles (a)
Genotype
Genetic description a trait based on a pair of alleles (BB)
Phenotype
Physical appearance/description of a trait
Homozygous
Genotype w/ same pair of allele (purebred)
Heterozygous
2 different types of alleles in genotype (hybrid)
Parental Cross
Pure dominant crossed with pure recessive
Principle of Segregation
Pairs of alleles separate during gamete formation
Principle of Independent Assortment
Each pair of alleles separate independently during gamete formation
Dihybrid cross
Genes fro two traits are independent
Probability
Mathematical science that predicts the chance a certain event will occur
Rules of multiplication
The change that two independent events will occur together is the product of their chances occurring separate
Does chance have memory?
No. A change event is not affected by previous events.
Trihybrid Cross
3 traits at the same time
Wild type
The phenotype most commonly found in nature
Self-fertilization
Fusion of sperm and egg that are produced by the same individual organism
Cross fertilization
Fusion of sperm and egg derived from two different individuals
Hybrids
The offspring of parents of two different species or of 2 different varieties of 1 species
- the offspring of 2 parents that differ in 1+inherited traits
- an individual that is heterozygous for 1+ pairs of genes
Cross (hybridization)
Cross fertilization of 2+ different varieties of an organism or of 2 different species
P Generation
Parent individuals from which offspring are derived in studies of inheritance
F1 Generation
Offspring of 2 parental (P Gen) individuals
F2 Generation
Offspring of the F1 gen
What are the 4 hypothesis of Mendel?
1) There are alternative forms of genes, the units that determine heritable traits
2) For each inherited characteristic, an organism has two genes, one from each parent. These genes may both be the same allele, or they may be different alleles
3) A sperm or egg carries only 1 allele for each inherited trait, b/c allele pairs separate (segregate) from each other during the production of gametes, and each contribute an allele to offspring
4) when the two genes of a pair are different alleles and one is fully expressed while the other has no noticeable effect on the organism’s appearance.
Punnet Square
A diagram used in the study of inheritance to show the results of random fertilization
Test Cross
The mating b/w an individual of unknown genotype for a particular characteristic and an individual that is homozygous recessive for that same characteristic
Rule of Addition
The probability that an event can occur in two+ alternative ways is the sum of the separate probabilities of the different ways
Which is more common? Recessive or dominant?
Recessive
Carriers
An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder
Cystic Fibrosis
A genetic disorder that occurs in people w/ 2 copies of a certain recessive allele characterized by an excessive secretion of mucus and consequent vulnerability to infection
- common for European ancestry
- probability increases with close relative mating
Achondroplasia
A form of human dwarfism caused by a single dominant allele
Huntington’s Disease
Human genetic disorder caused by a dominant allele characterized by uncontrollable body movements and degeneration of nervous system
Amniocentesis
A technique for diagnosing genetic defects while a fetus is in the uterus
- a sample of amniotic fluid, obtained via a needle inserted into the union is analyzed for telltale chemicals/defective fetal cells
- 14 to 16 week
Chorionic villus sampling
A technique used for diagnosing genetic defects while the fetus is in the uterus
- a small sample of the fetal portion of the placenta is removed and analyzed
- 8 to 10 week
Ultrasound Imaging
A technique for examining a fetus in the uterus
- high frequency sound waves choking off the fetus are used to produce an image of the fetus
- 18 week
Fetoscopy
A technique for examine a fetus for anatomical deformities
- a needle-thin containing a viewing scope is inserted into the uterus, giving a direct view of the uterus
Incomplete Dominance
A type of inheritance in which the phenotype of a heterozygote is intermediate b/w the phenotypes of the 2 types of homozygote
Why is relationship of genotypes to phenotypes rarely simple?
No complete dominance, 2+ alternative alleles for gene, genotype doesn’t always indicate phenotype
ABO blood groups
3 alleles produce 4 phenotypes (A, B, O, AB)
Codominance
Expression of 2 different alleles of a gene in a heterozygote
Pleiotropy
The control of more than 1 phenotypic characteristic by a single gene
- ex. sickle cell
Genetic screening
Testing people for alleles associated w/ a particular genetic disorder
Polygenic inheritance
The additive effect of 2+ gene loci on a single phenotypic characteristic
- ex. skin color
Recombination frequency
w/ respect to 2 given genets, the # of recombinant progeny from a mating divided by the total # of progeny
- carry combinations of alleles different from those in either of the parents as a result of independent assortment of chromosomes or crossing over
Sex Chromosome
A chromosome that determines whether an individual is male or female
- XX, XY
Monoecious
Having individuals that produce both sperm and eggs (usually refers to plants)
Hermaphroditic
A condition in which an individual has both female and male gonads and functions as both a male and female in sexual reproduction by producing both sperm and eggs (animals)
Sex-Linked Gene
A gene located on a sex chromosome
Red green color blindness
A category of common, sex-linked human disorders involving several genes on the X chromosomes
- characterized by a malfunction of light-sensitive cells in the eyes
- affects mostly males but also homozygous females
Hemophilia
A human genetic disease caused by a sex-linked recessive allele, characterized by excessive bleeding following injury.
Duchenne muscular dystrophy
A human genetic disease caused by a sex-linked recessive allele
- characterized by progressive weakening and a loss of muscle tissue
