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10.1 Genetics developed from curiosity about inheritance. I. The Blending Hypothesis of Inheritance. A trait is a variation of a particular characteristic such as for red flowers or yellow flowers
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B. When Mendel crossed plants that differed in only one-trait it was called a mono-hybrid cross
3. When only one of the alleles in a heterozygous individual appears to affect the trait, that allele is called the dominant trait. The allele that does not appear to have an affect on the individual is called the recessive trait
4. The two alleles for a character separate during the formation of gametes, so each gamete carries only one allele for each character. This is known as Mendel’s Principle of Segregation
Brown male X
Man’s parents: Bb
Kids: Bb or bb
2. The ability to taste the chemical PTC is determined by a single gene in humans with the ability to taste given by the dominant allele T and inability to taste by the recessive allele t. Suppose two heterozygous tasters (Tt) have a large family.
b. 3/4, 3/4
RrYy x RrYy
3. In pepper plants, green (G) fruit color is dominant to red (g) and round (R) fruit shape is dominant to square (r) fruit shape. These two genes are located on different chromosomes.
a. What gamete types will be produced by a heterozygous green, round plant?
b. If two such heterozygous plants are crossed, what genotypes and phenotypes will be seen in the offspring and in what proportions?
9 Green, round
3 Green, square
3 Red, round
1 Red, square
4. A hybrid pink CRCW snapdragon was crossed with a pure white one CWCW. Red flower color is incompletely dominant.
CR CW :CW CW
5. Paul is blood type O. His father was blood type A and his mother was blood type B. What were the genotypes of his parents and what are the possible blood types and ratios expected for crosses involving these parental genotypes?
IAi and IBi
1= Darkest 6=Lightest
A. Biologists worked out the processes of mitosis and meiosis in the late 1800s and observed the parallels between the behavior of chromosomes and the behavior of Mendel’s heritable factors
B. The chromosome theory of inheritance states that genes are located on chromosomes, and the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns
C. The alleles for a gene reside at the same location or gene locus
C. The closer the two genes are on a chromosome, the greater the genetic linkage
A. Many species have sex chromosomes, designated X and Y that are associated with determining an individual’s sex XX= Female, while XY= Male
B. Any gene located on a sex chromosome is called a sex-linked gene
C. Sex-linked genes were discovered by Thomas Hunt Morgan while studying fruit flies
A. A number of human conditions, including red-green color blindness and hemophilia are inherited as sex linked recessive traits
B. It takes two copies of the allele to be present in females for them to show signs of the disorder while it only takes one in males
7. A color blind father and a mother who carries the color blind trait (b) have a boy and a girl. What are the percent chances of the children being color blind? A carrier for color blindness?
50% color blind
A. Trisomy 21 results in having three number 21 chromosomes
B. In most cases, a human embryo with an abnormal number of chromosomes results in a miscarriage
C. People with trisomy 21 have Down syndrome, named after John Langdon Down
A. Nondisjunction is when homologous fail to separate
B. A woman’s age will have an effect on the possibility of nondisjunction occurring
C. This is due to the time line of egg cell development
A. Duplication is when part of a chromosome is repeated
B. Deletion is when a fragment of a chromosome is lost
C. Inversion involves reversing a fragment of the original chromosome
D. Translocation occurs when a fragment of one chromosome attaches to a non-homologous chromosome
A. Single genes may move from one location to another in a chromosome or to a different chromosome
B. This was discovered by Barbara McClintock in the 1940’s
C. These genes can land in the middle of other genes and disrupt them
D. These genes are called transposons
A. There are over one thousand genetic disorders that are inherited as a dominant or recessive trait controlled by a single gene
B. Most human genetic disorders are recessive
C. A carrier is an individual who has a copy of the recessive disorder but does not show symptoms
Recesssive, only those ff colored.
Heterozygous, or carrier
What are the percent chances?
25% FF 50% Ff
A. Dominant alleles that are lethal are more common than lethal recessives
B. Usually, the person with the dominant disorder dies before the allele can be passed on
A. Sex-Linked alleles are usually located on the X Chromosome in humans
B. A male only needs to inherit one copy of the allele to exhibit the trait
C. A female must inherit two copies of the allele to exhibit the trait
Draw a pedigree for the punnett square. Children: 2 older boys are deaf. 2 younger girls are carriers.
A. A genetic counselor is trained to collect and analyze data about inheritance patterns
B. This information is used by couples to determine the risks of passing on genetic disorders to their children
C. Genetic tests are done before and after the baby is born