Chapter 7 - Inheritance Flashcards
What are the 2 factors that mae us resemble our parents
Nature and nurture
What is heredity
the passing of characteristics from parents to offspring
What is selective breeding
choosing which strands we mate together to obtain certain characteristics in the offspring
What is segregation
youve got two copied of each gene but only one copy is put into each gamete during meiosis
Give two examples of single gene traits
Fur length in cats
Coat color in cats
What is a single gene trait
A trait controlled by only one gene
Give two examples of multiple gene traits
eye color, skin color
Which plant did Mendel used for his experiments?
Pea plants
What did Mendel was looking for in his experiments?
Looked for “true breeding plants”: when you breed them together, they always give the same offspring (ex all purple flowers)
How are called Mendel’s “true breeding” plants?
Homozgous
What happened when Mendel tried to cross true breeding purple plants w true breeding white plants? Why?
- Got only purple flowers offspring
- Why? Because the purple trait is a dominant trait, and the white one is recessive (dominant always wins over recessive)
- In the “grandchildren” of this breeding, white flowers came back
How do we write dominant alleles? Recessive?
Dominant allele = always uppercase
Recessive allele = lowercase
What is a homozygous gene?
One that has only 1 recessive or dominant allele twice
What is a heterozygous gene?
Has 1 dominant allele and 1 recessive
How are dominant or recessive genes transferred to offspring?
Each parent puts into every gamete a single set of instructions for building the trait
Offspring receives 2 copies and the expression of the trait depends on the combinations of genes that this organism has for a specific locus
What is Mendel’s law of segregation?
The principle that during the formation of gametes, the two alleles for a gene separate, so that half the gametes carry one allele, and half the gametes carry the other
What is a Punnett square?
A diagram tracing the outcomes of a cross between 2 individuals
What are the steps to making and understanding a Punnett square?
Step 1: make sure the genotypes are ok (ex: mm, and MM)
Step 2: figure out which gametes they can produce (ex: m and m, and M and M)
Step 3: analyze possible combinations (ex: 1/4 homozygous dominant, 2/4 heterozygous Mm, etc)
Every fertilization outcome is different than the other (independent events)
Why is it not always possible to determine a genotype by observing the phenotype?
Because more than one gene might be involved in the part of the phenotype observed (ex skin color)
What can we do when we do not know the genotype of a parent? How is that called?
We cross (i.e., mate) an individual exhibiting a dominant trait but whose genotype is unknown with an individual that is homozygous recessive. Then we examine the phenotypes of their offspring. This is called a test-cross Also, we can guess which parents had which genotype depending on who has the condition or not and if it's recessive or dominant
What is a pedigreed animal?
One that we know its family tree (therefore can guess its genotype more easily)
What is incomplete dominance?
The case in which the heterozygote has a phenotype intermediate between those of the two homozygotes; an example is pink snapdragons, with an appearance intermediate between that of a homozygote for white flowers and a homozygote for red flowers.
How do we write incomplete dominance in Punnett squares?
(in example of red and white flowers) -
C(exposant)w C(exposant) r; why? Because upper-case and lower-case are only for 100% dominant or recessive genes
What would happen if we bred 2 CwCr pink flowers (incompletely dominant)
1 red (CrCr), 1 white (CwCw) and 2 pink (CwCr)
