Download Chapter 11 Notes: Mendelian Genetics

Chapter 11-1 and 11-3 Notes: Mendelian Genetics (and a bit of Ch. 14)
Genetics is ________________________________________________________________________
I.
History
a. Gregor Mendel was an _________________________________________ who was in charge of the
monastery garden. Being bored with mundane tasks, Mendel began studying pea plants. It’s a good thing
he chose Pea plants to study because:
i. They are ____________________________.
ii. He had different pea plants that were true-breeding. True-breeding means that if the plants selfpollinate they produce offspring identical to each other and the parents. True breeding means they
are _______________________ for that trait.
iii. He developed a technique of producing seeds from a process called cross-pollination, in which he
__________________________________________________________. He was in control of
which plants crossed with each other.
II.
Genes and Dominance
a. Trait: _____________________________________________________________________.
b. Mendel studied seven different pea plant traits including:
i. seed shape, seed color, seed coat color, pod shape, pod
color, flower position, plant height.
c.
Mendel studied two _________________, or different versions, of
each trait (wrinkled or smooth pea shape, green or yellow seed
color, etc.)
i. When discussing generations’ traits, we label them as
following:
1. The true-breeding parental generation is called the
“_____________________________”.
2. The offspring of the two parental plants is called the
“______ generation”.
3. A cross between F1 generation would be called “_________ generation.”
III.
Mendel’s Investigations
Mendel wanted to cross (or breed) two plants with different versions of the same trait. He wanted to know if the
characteristics of the plants were blended in the offspring.
a. He saw that when he crossed plants with different characteristics of the same trait (P), the trait in the F1
offspring was ______________________________.
b. The F1 plants resembled only one of the parents
c.
Mendel concluded:
i. Biological inheritance is determined by “_____________” that are passed from one generation to the
next.
1. Factors were later defined as “__________________”
2. Mendel discovered all of this without the knowledge of ______________!
ii. There was one gene for each trait.
For example, there was one gene for plant height. But, we know now that there are two versions of
this gene: one for a tall plant and one for a short plant.
d. Alleles: ___________________________________________________________________
i. Remember, genes are used to make ________________.
ii. Each allele contains the ____ that codes for a slightly different version of the same protein
iii. This gives us the different ______________________________ for each trait
e. Principle of dominance: Some alleles are dominant and some alleles are recessive.
i. Recessive alleles are able to be_______________________
ii. Dominant alleles _______________ recessive alleles
iii. The trait that was represented in the F1 generation was the ___________________ trait.
1. How many alleles do you have for each gene? ________
2. Where do the two alleles come from? ___________________________________
f.
Segregation:
i. Observation: After seeing that his F1 plants looked like only one plant of the P generation, Mendel
wanted to know what happened to the recessive alleles.
ii. Question: Did they disappear?
iii. Experiment: Mendel ___________________ the F1 plants to produce the F2 generation.
iv. Results from his F1 crosses: Both versions of the initial P traits _____________________ in the
_____ plants. The recessive allele was still there!
v. About ___ (or ¼) of the F2 plants
exhibited the recessive version of the
trait. (short plant)
vi. The dominant phenotype (tall plant)
was found in ______ (or ¾) of the F2
P
F1
F2
plants.
vii. Segregation of alleles during meiosis: When the F1 plants produce ______________ (sex cells)
and self-pollinate, the two alleles for the same gene ____________________ so that each gamete
carries the information for only one of the traits
1. Remember, gametes are ______________.
2. “____” to represents the dominant allele. (tall)
3. “____” to represent the recessive allele. (short)
4. Each gamete has only ______________ for each trait.
g. Law of Independent Assortment: Genes for each trait can be inherited ___________________ from each
other. For example
i. not all tall plants have green pea pods
ii. not all people with _______________________________________.
Key Terms in Mendelian Genetics: SEE FUNDAMENTALLY GENETICS ACTIVITY
IV.
Beyond dominant and recessive alleles
There are some exceptions to Mendel’s principles. Luckily, none of these exceptions are exhibited in pea plants.
If so, Mendel would not have been able to figure out inheritance.
a. Some ______________ are neither dominant nor recessive.
i. _______________________: situation in which one allele is not completely dominant over another;
the phenotype is a “___________” of the two alleles
Example: In some plants, when a true-breeding plant with _______ flowers is crossed with a truebreeding plant with ________ flowers, _________ flowers are produced. Neither red nor white is
dominant over the other.
ii. __________________: situation in which both __________ of a gene contribute to the phenotype of
the organism; both alleles are expressed but ________ blended
Example: In cows, the allele for red fur is _____________ with the allele for white fur.
______________ cows carrying one red and one white allele have ________ fur, known as
________.
b. Many traits are controlled by multiple __________ or multiple ___________.
i. Multiple alleles: where _______________________________________ of the same gene exist.
1. Remember, an organism will have only __________________________ (one from mom and
one from dad).
2. Examples: ______________________________________________________________
ii. Polygenic traits: traits that are determined by alleles
from ____________________; these traits usually
have a range of phenotypes
1. Examples:
_____________________________
V.
Sex Determination:
a. There are two types of chromosomes.
i. ___________________________: Of the 46
chromosomes, 44 of them (22 pairs of chromosomes) are
called autosomes (______________________ chromosomes).
ii. Sex chromosomes: The last two chromosomes are called the
sex chromosomes because they determine the
_________________________. Females have two X
chromosomes (_____) and males have one X and one Y
chromosome (_____).
b. Gametes
i. All gametes are __________________. In humans, that
means each egg cell and each sperm cell has 1 copy of each chromosome for a total of 23
chromosomes.
1. Egg cells: All human egg cells carry ________ chromosomes, one of which is a single
__________________________. This is written as _________________.
2. Sperm cells: In males, there are two types of sperm cells- one carries an X chromosome
(________) and one carries a Y chromosome (________).
3. When a sperm and egg cell combine, half of the time the fertilized eggs (also called
_______________) are female (_________) and half of the time they are male
(__________).
VI.
Sex Linked traits: traits that are determined by alleles that are _____________________________.
a. The Y chromosome is shorter and does not
_______________________
b. Females are XX and males are XY.
c.
Females can be _______________ or _________________ for a
trait carried on the X chromosome, but males (having only one X
chromosome) are _______________________.
i. If they inherit a defective gene from the parent, then they
will _________________________ because they cannot
inherit a second gene to mask it.
ii. Conversely, a healthy male cannot be
__________________________________ because they only have one X chromosome.
VII.
Mapping Genes
a. It’s easy to imagine that genes on different chromosomes assort independently, but what about genes that
occur on the same chromosome? Don’t they always appear together?
b. Not always due to ___________________.
c.
Genes that occur together on a chromosome will be separated when homologous chromosomes exchange
genes.
d. The _________________ of genes occurring together can help us generate a ________________.
i. The more often two genes occur together, the _________ they are to each other on the
chromosome.
ii. If the genes are never separated by crossing over, they always occur together. All offspring will look
like _____________________ (in reference to the genes in question).
iii. If half of the offspring are _________ and half are ________________________ (in reference to the
genes in question), then they are said to be __________________. This means they are either on
separate chromosomes or they are almost always separated during meiosis.
iv. You will learn to calculate distances and create a map in AP Bio, or in college
VIII.
Genetics and the Environment: Characteristics are determined by both __________ and the
________________________________.
a. External: While genes will influence the height of a plant, the amount of __________, ________, and other
__________________________ will also affect the height.
b. Internal: There are recent findings that proteins involved with DNA can ____________________ based on
environmental factors.
i. Certain chemical exposure can turn genes on or off (make the traits show up or not) for generations
after exposure, but there are no changes to the DNA (no _______________).
ii. This new understanding of how genes are expressed is called _____________________.