11 notes Flashcards
Mendels 3 laws
- Law of independent assortment
- Law of segregation
- Law of dominance
4 ways beyond mono hybrid crosses that alleles / genes combine?
- Incomplete dominance: red + white = pink
- Codoninance: black + white = black/white
- Multiple alleles:
- Polygenic traits:
Body cells are also…
Somatic and mitosis
Sex cells
Gametes
What other two words are used for crossing over
Synapsis and Recombination
Different forms of a gene are called…
Alleles
Different forms of a gene are called…
Alleles
If a homozygous tall pea plant and a homozygous short pea plant are crossed…
No hybrids are produced.
A Punnet square is used to determine the…
The probable outcome of the cross
Organisms that have two identical alleles for a particular trait are said to be…
Homozygous
The physical characteristics of an organism are is…
Phenotype
A situation in which a gene has more than two alleles is known as
Polygenic dominance
Unlike mitosis, meiosis results in the formation of…
Four haploid gamete cells
To maintain the chromosome number of an organism, the gametes must…
Become diploid
A gene map shows…
The relative locations of genes on a chromosome
List the four basic principles of genetics that Mendel discovered with his experiments
The law of independent assortment (traits), law of segregation (separation), law of dominance (alleles), and law of probability.
What is probability and how does it relate to genetics?
Probability is the likelihood that a particular event will occur and it can be used to predict the outcomes of genetic crosses.
How do multiple alleles and polygenic traits differ?
Multiple alleles is a gene with more than two alternatives.
Polygenic traits is when more than one gene controls one trait.
Why can multiple alleles provide many different phenotype so for a trait?
Multiple allies can provide many different phenotype so because there are more combinations of alleles causing more variations.
Are an organisms characteristics determined only by its genes?
No because the environment can also affect its characteristics.
Compare meiosis I with meiosis II in terms of the number and arrangement of chromosomes
Meiosis I: all the chromosomes are doubled and consist of duplicate chromosomes.
Meiosis II: the sister chromatids separate to produce four haploid daughter cells.
Explain why it is chromosomes, not individual genes, that assort independently.
It is the chromosomes that are separated during meiosis. The genes are located on the chromosome.
The scientific study of heredity is called ________
Genetics
Describe Gregor Mendel’s peas
When pollen fertilizes an egg cell, a seed for a new plant is formed. Pea plants normally reproduce by self-pollination.
What does it mean when pea plants are described as being true-breeding?
If they were allowed to self-pollinate they would produce offspring identical to themselves
To preform his experiments, how did Mendel prevent pea flowers from self-pollinating and control their cross-pollination?
He joined male and female reproductive cells from two different plants.
State the principle of dominance
That some alleles are dominant and others recessive
What traits were controlled by dominant alleles in Mendel’s pea plants?
Tall and yellow
How did Mendel find out whether the recessive alleles were still present in F1 plants?
He crossed the F2 generation with itself to produce the F2 offspring.
About one fourth of the F2 plants from Mendel’s F1 crosses showed the trains controlled by the _________ allele
Recessive
Mendel’s explanation of the results from his F1 cross
Mendel assumed that a dominant allele has masked the corresponding recessive allele in the F1 generation.
At some point, the allele for shortness was segregated, or separated, from the allele for tallness.
What are gamets?
Specialized cells involved in sexual reproduction.
What is the probability that a single coin will come up heads?
50% or 1/2
Why can the principles of probability be used to predict the outcomes of genetic crosses?
The way in which alleles segregate is completely random.
How do geneticists use Punnet squares?
They are used to predict and compare the genetic variations that will result from a cross.
I’m Mendel’s model of segregation, what was the ratio of tall plants to short plants in the F2 generation?
3:1
The _____ the number of offspring from a genetic cross, the closer the resulting numbers will get to expected values
Larger
How can you be sure of getting the expected 50:50 from flipping a coin?
You flip multiple times
List the two things that Mendel’s principles of genetics required in order to be true.
A. Each organism must inherit a single copy of every gene from both its “parents”
B. When an organism produces its own gamets, those two sets of genes must be separated from each other so that each gamer contains just one set of genes.
What does it mean when two sets of chromosomes are homologous?
Each of the 4 chromosomes that came from the male parent has a corresponding chromosome from the female parent.
Describe a diploid cell
2N
Contains two sets of homologous chromosomes
The number of chromosomes in a haploid drosophila cell
4
Why is meiosis described as a process of reduction division?
The number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
What are the two distinct division of meiosis?
Meiosis I and Meiosis II
How does a Tetrad form in prophase I of meiosis?
Each chromosome pairs with its corresponding homologous chromosome to from the structure called a Tetrad
How many chromatids are in a Tetrad?
4
What results from the process of crossing-over during prophase I?
It results in the exchange of alleles between homologous chromosomes and produces new combinations of alleles.
