Theme 4A Flashcards
What are alleles
“Alternate” forms of genes
What are genes
Basic hereditary unit passed from parents to offspring
How does gene and allele expression affect phenotypes
The combination of genes controls what proteins are produced, proteins affect the allele and the combination of alleles at a specific locus affects the phenotype
What is a monohybrid cross
Cross between two heterozygotes (for a single gene)
75% chance of dominant phenotype
25% chance of recessive phenotype
What is a test cross
Used to determine whether individuals with dominant phenotype is homozygous or heterozygous
“Tester”: homozygous recessive
How does meiosis determine the frequency of gametes of homozygous and heterozygous individuals
Segregation of alleles reflects the separation of chromosomes in meiosis , happens during anaphase 1
What are dominant and recessive alleles
Dominant: codes for a functional protein
Recessive: doesn’t
What is incomplete dominance
Intermediate phenotype exhibited by heterozygotes, produces some functional enzyme but not full amount (eg. grey if A=black and a=white)
What the genotype and phenotype ratios for incomplete and codominance
1:2:1
What is codominance
Both traits expressed in heterozygotes (eg. both black and white, not grey)
What is blending inheritance
Offspring have traits that are intermediate to their parents
What would happen to variation if blending inheritance was the mechanism
Variation would be reduced
What is Mendel’s hypothesis
Adult plants carry two copies of genes that govern the inheritance of a character
If the pair has two different genes, the dominant gene masks the recessive gene
Diploid organisms get one allele from each parent
What is a trait
Variation in a character
Why did Mendel use true breeding garden peas for his experiment
Can be grown easily without elaborate equipment
Gametes are produced in the structures of the flowers
Male gametes are in the pollen and female gametes are in the carpel
Mendel prevented self fertilization by removing the anthers
