Inheritance Flashcards
How does genetic variation translate to phenotypic variation?
- Gregor Mendel (Born in Austria, became a monk)
- Observation : Individuals vary for different characteristics of an organism
Genotype-
Set of genes in our DNA responsible for a certain trait.
Phenotype:
Physical expression or characteristics of that trait.
Blending hypothesis:
Different phenotypes blend to uniformity over time.
-Differences in phenotypes amount individuals are lost in offspring and cannot reappear in the population.
True Breeding:
Offspring produced by self-pollination always have a given feature of the parent plant.
Self-pollinating:
An individual plant that can produce both gametes(sperm and egg) and fertilize itself to produce offspring.
Meiosis:
Cell division process that produces sex cells(gametes)
-Homologous chromosomes
•diploid parent cells are reduced to haploid sex cells.
Step 1 Meiosis:
Start with diploid parent cell
Homologous chromosomes
1 of each paternal & maternal sex cells (gametes)
Paternal 23 and Maternal 23 = 46 chromosomes
Step 2 Meiosis:
The Chromosomes duplicate
Step 3 Meiosis:
First Cell Division
• Homologous Chromosomes separate
* Two daughter cells
Step 4 Meiosis:
Second Cell Division
• sister chromatids separate
* four haploid daughter cells
Dominance Patterns:
Dominant allele:
determines an organism’s phenotype will be expressed even if an individual has only copy of the dominant allele.
Dominance patterns:
Recessive allele:
recessive phenotype masked by dominant phenotype; recessive phenotype only expressed if 2 copies of recessive allele.
Simple Dominance:
When two different alleles are present in an individual, one allele is dominant and one is preferably expressed.
Combination of alleles for a trait:
genotype
ex
Dominant genotype= AA,Aa
Recessive genotype = aa
Molecular Basis of dominance:
- DNA codes for proteins – Different alleles may code for different versions of proteins or absence of proteins
- Type, function, presence/absence of protein determines phenotype
- Dominant allele: allele of this phenotype is fully expressed
- Recessive allele: allele of this phenotype is masked in presence of dominant allele
homozygous (dominant) genotype:
AA= Dominant alleles
homozygous (recessive) genotype:
aa= recessive alleles
Heterozygotes genotype:
Aa= 1 dominant and 1 recessive alleles
Punnett squares:
Powerful predictive tool,
Can determine the probability of the offspring inheriting genetic disorders based on parent’s genotype and dominance.
Codominance:
heterozygotes express the phenotype of both alleles.
Incomplete Dominance:
Heterozygotes express a third unique phenotype that is an intermediate between the dominant and recessive phenotype.
Epistasis:
the expression of one gene’s phenotype is affected by the expression of a second gene.
Discrete Variation:
organisms vary in traits that can be broken into categories on an “either or” basis.
Continuous variation:
organisms vary in traits along a continuum
- Can’t be explained by single-gene mechanism.
Polygenic Inheritance:
phenotype is controlled by the additive effects of two or more genes.
Pleiotropy:
1 gene affects many different characteristics.
• characteristics often seem unrelated to one another.
If the blending model of inheritance is correct, which of the following outcomes would you expect from the hybridization below?
Purple, White or light purple.
Light purple
Is Huntington’s Dominant and Recessive?
Dominant
Is Tay-Sachs Dominant or Recessive?
Recessive
Which of the following accurately describes the outcome of Mendel’s F1 X F1 cross?
If the maternal and paternal Ff•Ff
75% of the F2 generation will display the dominant phenotype; 50% of the F2 will be homozygotes, 50% will be heterozygotes.
Question: the couple’s first child is NOT a carrier. Is the couple’s second child more likely to inherit the t allele as a result?
True or False.
False
What genotype must a dog have to be chocolate?
BB, Bb, or bb.
Ex.
bb=(recessive) homozygous
Based on the dominance patterns for coat color and pigment deposition alleles, which of the following genotypes would result in a yellow lab puppy?
BBEe, Bbee, BBee, or BBEe
Bbee or BBee
Ex.
The (e) gene is recessive so in order to affect the coat color the alleles has to express ee = Yellow color.
