Ch. 14 and 15 Review Flashcards
What is the blending model of inheritance?
Genetic material mixes from paternal and maternal genes. Like mixing paint.
Why did Mendel use peas?
-are eukaryotes
-multicellular
-reproduce sexually and asexually (cross and self pollination)
-cheap, easy to handle
-short generation time
-obvious characteristics and varieties
True breeding produces offspring _____ the parent
like
What was Mendel’s first experiment?
Mixing true breeding pea parents via cross pollination, then allowing the F1 generation to self pollinate
What conclusions did Mendel draw from his first experiment (5)
- characters are produced by “heritable factors” (genes) that are discrete (unchanging)
- An organism had two genes for each character, one from each parent
- Alleles have alternate versions
- When different alleles are together:
dominant allele- affects appearance
recessive allele- has no effect on appearance - Alleles separate during gamete production LAW OF SEGREGATION
What happens first when making offspring?
The law of segregation
parent must give one allele only
Define phenotype and genotype
Phenotype- physicial appearance of an organism
Genotype- genetic makeup
Define homozygous and heterozygous
Homozygous- having identical alleles for a gene pair
Heterozygous- having different alleles for a gene pair
Define monohybrid and dihybrid crosses
Monohybrid- parents differ in one character (gene)
Dihybrid-parents differ in two characters (genes)
What were Mendel’s 2nd experiment conclusions
Law of independent assortment
a pair of alleles may sort to gametes independently of other pairs of alleles
meiosis sorts homologous chromosomes randomly during meiosis 1
ONLY true for genes on DIFFERENT chromosomes
What are some examples of dominance?
Complete dominance- flower color in pea plants
Incomplete dominance- flower color in snap dragons
Codominance- AB blood type
How many distinct alleles can one person have?
Only 2 different alleles
Do dominant alleles mean most common?
NO, an example would be pea color, dominant color is yellow
Why do some traits have many alleles?
Some phenotypes result from more than one gene, polygenetic inheritance
ex. skin color
Phenotype is the result of the genotype and the ________
environment
Mendel observed _________ not chromosomes. Who observed chromosomes?
characters, Thomas Hunt Morgan
What did Morgan study in fruit flies?
Eye color, body color, wing shape
Wild type vs mutant type
wild type- typically found in nature (normal)
mutant type- occurs when mutation produces a new allele
What was Morgans experiment 1, what were the conclusions?
Crossing between red and white eyed flies
conclusions- red allele is dominant to white, eye color is linked to sex (X linked)
In Morgans first experiment, which parents allele determined eye color?
Females
For X linked genes, who usually shows this gene?
males
Explain Morgan’s second experiment
Morgan crossed true breeding wild type and mutant type flies in a dihybrid cross
body color- gray (b+), black (b)
wing shape- normal (vg+), vestigial (vg)
Explain Morgan’s second experiment conclusions?
The genes for body color and wing shape appear to be linked
independent assortment does not apply
however, linked genes can be unlinked by crossing over
What differed on Morgan’s dihybrid cross from Mendel’s?
Morgan crossed the F1 generation with a true breeding black vestigial
Mendel self pollinated
