Introduction to Mendel and the Gene Flashcards
What did Mendel work with to figure out the rules of inheritance?
garden peas
What is blending inheritance?
parental traits blend; offspring have intermediate traits
Black sheep + white sheep = gray sheep
What is Inheritance of acquired characteristics?
parental traits are modified through use and passed on
- Giraffes stretch their necks, offspring end up with longer necks
Why did garden peas make a good model organism for Mendel’s work?
a species used for research
Practical to work with
Conclusions drawn from them can be applied to other species
They have several polymorphic traits
inexpensive
easy to grow
short generation time
How did Mendel control mating in his pea experiments?
Peas normally self-fertilize (self-pollinate) so Mendel prevented self-pollination by removing the male organs from a flower before pollen formed
he used cross-pollination
What is cross pollination?
It collects pollen from one individual and transfers it to the female organ on another plant whose male organs have been removed
What traits did Mendel study?
seven traits and each of the traits had two distinct phenotypes
What were the seven traits?
Seed shape
Seed color
Flower color
Flower position
Plant height
Pod shape
Pod color
What is a reciprocal cross?
To determine if biological sex (male vs. female) influenced inheritance, Mendel performed a reciprocal cross
Mother’s phenotype in 1st cross is father’s phenotype in 2nd cross
Father’s phenotype in 1st cross is mother’s phenotype in 2nd cross
What is the law of segregation?
Segregate into different gamete cells during the formation of eggs and sperm in the parents
happens in meiosis I
What is the law of independent assortment?
alleles of different genes are transmitted independently of each other
four possible phenotypes should be shown in a 9:3:3:1 ratio
What is sex-linked inheritance?
occurs when a gene is located on a sex chromosome
What is autosomal inheritance?
occurs with genes on non-sex chromosomes
What is codominance?
Neither allele is dominant or recessive to the other
ex: ABO blood types
Incomplete dominance?
Heterozygotes have an intermediate phenotype
pure-line plants with red flowers (RR) crossed to pure-line plants with white flowers (rr) : Rr phenotype is a pink flower
How can the environment influence a phenotype?
with diet, temperature, oxygen levels, humidity, light cycle, lack of nutrients, and mutagens can all affect an organism
Example of environment influencing a phenotype
The human genetic disease phenylketonuria (PKU) is an example of a gene-by-environment interaction:
-Individuals with PKU are homozygous recessive for a gene that codes for an enzyme
Individuals placed on a low-phenylalanine diet develop
What are examples of quantitative traits?
human height and skin color
What is a quantitative trait?
a trait that varies continuously
What is a pedigree?
a family tree that is used to learn the mode of transmission for a given trait
What is an autosomal recessive trait?
is the phenotype is due to this, Individuals with the trait must be homozygous (i.e. ss) example: sickle cell disease
Unaffected parents of an affected individual:
Are likely to be heterozygous for the trait (i.e. Ss
Autosomal dominant trait?
Homozygous (HH) or heterozygous (Hh) individuals will display the trait
One heterozygous parent will pass it on to about half of his/or her offspring (kids are Hh or hh)
example: Huntington disease
What are X-linked recessive traits?
X-linked recessive traits are common
Men (XY) will exhibit the trait if they inherit it from their mothers
Women (XX) will exhibit the trait only if they are homozygous
Usually skips a generation
example: red-green colorblindness
What are X-linked dominant traits?
X-linked dominant traits are rare
An affected male passes the trait to all his daughters but none of his sons
Daughters receive his only X chromosome
A female carrier will pass the trait to half her daughters and half her sons
Both sexes receive one of her X chromosomes
