Chapter 7: Genetics

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What is genetics?
the study of heredity
When and where was Gregor Mendel born? What did he become? Where did he study scienec and mathematics? What did he study at the monestary?
1822 in what is now the Czech Republic; he became a priest; he studied at the University of Vienna; he was the gardener so he studied pea plants.
What is fertilization? What does it produce?

It happens during fertilization when male and female reproductive cells join.
It produces a new cell, which develops into a tiny embryo encased within a seed.
True or False: Pea flowers are normally self-pollinating, which means that sperm cells in pollen fertilize the egg cells in the same flower.
What does true-breeding mean? Are pea plants true-breeding?
Yes, pea plants are true-breeding meaning that if they were allowed to self-pollinate, they would produce offspring identical to themselves.
How did Mendel accomplish joining male and female reproductive cells from two different plants? What is this process called?
He had to prevent self-pollination. He cut away the pollen-bearing male parts and then dusting pollen from another plant onto the flower. This process is called CROSS-POLLINATION. This allowed Mendel to cross-breed plants with different characteristics, and then to study the results.
What is a trait? Mendel studied 7 traits. What are hybrids?

A trait is a specific characteristic
Hybrids - the offspring of crosses between parents with different traits
What were Mendel's two conclusions about why only one characteristics from a parent shows up?

1) Biological inheritance is determined by factors (genes which determine traits, but he did not know that) that are passed from one generationto the next
2) Mendel's conclusion called the principle of dominance. This states that some alleles are dominant and others are recessive.

What are alleles?
What is segregation?
What are gametes?

- different forms of a gene
- separation of alleles
- sex cells
What does homozygous/heterozygous mean? Which one is true-breeding? Which one is hybrid for a particular trait?

Homozygous means than an organism has two identical alleles, Heterozygous means they have two different alleles for the same trait.
Homozygous are true-breeding, Heterozygous are hybrid for a particular trait.
What does the principle of independent assortment state?

that genes for different traits can segregate independently during the formation of gametes. Independent assortment helps account for the many genetic variations in plants, animals, and other organisms.
As a result, if enough gametes are produced, the collective group of gametes will contain all combinations of alleles possible for that organism.
Summarize Mendel's Principles.

1) The inheritance of biological characteristics is determined by individual units knows as genes. Genes are passed from parents to their offspring.
2) In cases in which two or more forms (alleles) of the gene for a single traight exist, some forms of the gene may be dominant and others may be recessive.
3) In most sexually reproducing organisms, each adult has two copies of each gene - one from each parent. These genes are segregated from each other when gametes are formed.
4) The alleles for differenent genes usually segregate independently of one another.

What is Gregor Mendel known as?
What are his 3 principles (Mendelian Principles)?

"The Father of Modern Genetics"
Principle of Dominance, Principle of segregation, Principle of independent assortment
What was the early "Blending Theory"?
That the offspring combination of traits from both parents could never change (red flower + white flower = pink flower)
TRUE OR FALSE: Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or multiple genes.
What is incomplete dominance?
Cases in which one allele is not completely dominant over another one; The heterozygous phenotype is somewhere in between two homozygous phenotypes (In Mirabilis plants, a red one combined with a white one produces pink flowers because both of them are dominant, but not one is dominant over the other).
What is codominance?
In which both alleles contribute to the phenotype. For example, in certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens have a color described as "erminette," speckled with black and white feathers. This is NOT blending like incomplete dominance.
When a gene has more than two alleles, it is said to have ________.
multiple alleles... If there are 4 alleles, one is dominant to all others and and the other is dominant to 2 and the other is dominant to 1 and the other isn't dominant to any (if that made any sense)
What are polygenic traits?
Traits that are controlled by two or more genes
TRUE OR FLASE: The environment has an impact on characteristics in an organism.
What are linked genes?
genes on the same chromosome are joined together - "linked"
Do linked genes experience independent assortment?
What disrupts linkage groups and creates individuals with new gene combinations (recombinants)?
The more frequent the crossing-over, the _________
further apart the genes
Sex-linked genes are genes found ONLY _________.
on the X chromosome
Single gene has multiple phenotypic effects
Interaction of allele pairs (genes) controls expression of single trait
Polygenic inheritance:

- Trait shows a range or continuum of expression
- Additive effect of two or more genes (pairs of alleles) determines a single phenotypic character
- Example - height, weight, hair color, facial features, intelligence


- to determine the probability of two independent events occurring
- MULTIPLY the probability of one event occuring by the probability of the other event occurring

- Probability that any one of two or more mutually exclusive events will occur
- ADD together individual probabilities

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