Mendelian Genetics Flashcards Preview

Bio 100 (part 3) > Mendelian Genetics > Flashcards

Flashcards in Mendelian Genetics Deck (26)
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1
Q

What is blending inheritance?

A

Traits in the mother and father blend together to form the traits in their offspring. Source was mixing of blood.
White and black sheep produce gray sheep.
Analogy: Mixing of paints

2
Q

When did Mendel determine rules of inheritance?

A

1865

Not really known until 1900’s

3
Q

Who were Sutton and Boveri and what did they determine?

A

1903, Sutton and Boveri independently linked patterns of inheritance with chromosomes and reduction in chromosome number (meiosis) restored at fertilization.

4
Q

What did Thomas H. Morgan discover?

A

1907, T. H. Morgan and other biologists described details of sex determination by studying fruit flies.

5
Q

Why was Mendel successful?

A

Excellent observer and record keeper
Quantitative approach
Picked a really good model organism for his research (relatively easy to manipulate)
Some luck involved
The traits he studied were relatively simple and straightforward
The traits he studied happened to be unlinked with each other

6
Q

What are Mendel’s rules of inheritance?

A

units of inheritance are “particles of inheritance” (material elements) => genes are nucleotide sequences on DNA coding for proteins

particles of inheritance come in pairs that do not blend together => gene alleles come in pairs on homologous chromosomes and form definite traits

particles retain their character through generations => chromosomes replicate to be passed on to each following generation

particles of inheritance separate during formation of gametes => alleles on homologous chromosomes separate during meiosis I, ending in different gametes

7
Q

Define Character

A

Qualities or attributes of an organism that are visible or discernable (height to protein primary structure)
Ex: Seed shape, seed color

8
Q

Define Trait

A

Variations in a character

Ex: round, wrinkled, yellow, green

9
Q

Define genotype

A

Genetic makeup that determines trait of a character will be expressed

10
Q

Define phenotype

A

The visible or determinable expression of the genotype

11
Q

Define homozygous

A

An organism has two identical alleles of a gene for a given character

12
Q

Define heterozygous

A

An organism has differing alleles for a gene for a given character

13
Q

Define dominant

A

An allele that is expressed in the heterozygous condition

14
Q

Define recessive

A

An allele that is not expressed in the heterozygous condition

15
Q

Describe Mendel’s Law of Segregation

A

Mendel: the particles of inheritance for green and yellow color segregate but remain unchanged during reproduction

16
Q

Mendel’s Rules of Inheritance

A

Males and females contribute equally to the genotype of their offspring.
Some alleles are dominant to other alleles. (certain traits “recede” but are still present)

17
Q

Are homozygous alleles identical genetically?
Yes, both alleles express the same phenotype

No, the alleles will differ slightly in
DNA base pair code

A

Both are correct, the same phenotype can be expressed even though the underlying DNA sequence can be different (remember third position changes in DNA).

18
Q

How did Mendel disprove the idea of “blending” in heredity?

A

There was no “blending” of traits
no intermediate or transitional forms
therefore,
“particles of inheritance” that did not change
“pairs” that did not blend
“recessive” expressed only in absence of dominant

19
Q

How does a Punnet square work?

A

If you can’t figure this out you don’t deserve to pass the class >_<

20
Q

Punnet square example: a cross between Yy and Yy (monohybrid)
What is the phenotype in the next generation?
What is the genotype in the next generation?

A

Many more yellow than green the expected is 3:1 yellow versus green
1:2:1 ratio of homozygous yellow: heterozygous yellow and homozygous green

21
Q

Why would the actual counts of pea color only be expected to approximate the 3:1 ratio?
because science is not exact
because of experimental error
according to Mendel’s laws, there would be an exact 3:1 ratio

A

B is correct because some peas may be lost or miscounted, some will shrivel up and won’t be counted, etc.

22
Q

How does a punnet square work with dihybrid crosses?

A

Same as a normal punnet square but you have two variables like X and Y for the genotype

23
Q

Describe what is meant by incomplete dominance

A

Some traits appear to blend (in this case red and white snapdragon flowers)
A cross of red and white yields a F1 generation of all pink.
The F2 generation will have a 1:2:1 ratio of red:pink:white
Genotypic and phenotypic ratios are the same for incomplete dominance

24
Q

Describe what is meant by codominance.

A

There are A, B, AB and O blood types in humans
A means one kind of surface protein on red blood cells, B another and O means that cells lack both A and B.
AB blood has both
Both A and B are dominant to O
Presence of A and B alleles means that both proteins are expressed
An individual can only have two alleles for these blood types

25
Q

Understand what is meant by multigenic (or polygenic traits)

A

Multigenic traits are controlled by a series of genes.
Examples in humans include skin color, height, certain diseases like susceptibility to heart disease and complex behaviors (extroversion, schizophrenia)
The phenotypes approximate a bell shaped curve and variation appears to be smooth or continuous.

26
Q

Why is color blindness more prevalent in men than women?

A

Because it is an allele located on the X sex-chromosome. It is a recessive allele so since men only have one X chromosome it is easier to occur. Women have two X chromosomes so both would need to have the recessive allele for color blindness