14 Mendel and the gene idea

Question 1

What is a character? Give an example.

Answer 1

It’s a heritable feature that varies among indivduals. Example would be flower colour

Question 2

What is a trait? Give an example.

Answer 2

A trait is a variant of a character, such as purple or white colour for flowers. they are characterisitcs defined by genes

Question 3

What is the haploid reproductive unit of plants?

Answer 3

Spores

Question 4

How do pollen plants self-fertilize?

Answer 4

Pollen grains from the stamen fall on the carpel of the same flower and the sperm released from the pollen grains fertilize the egg in the carpel.

Question 5

What are the reproductive organs of a flowering plant?

Answer 5

They’re in the flower itself. The pollen-producing organs are called stamens. The egg-bearing organs are called carpels

Question 6

How did Mendel cross (mate) pea plants?

Answer 6

He removed the immature stamen from a purple flower, and transferred sperm-bearing pollen from stamens of a white flower to carpel of purple. The pollinated carpel turned into a pod, whose seeds Mendel planted.

Question 7

What is a true-breeding plant?

Answer 7

they are a variety that over many generations of self-pollination have produced only the same variety as the parent plant.

Question 8

What is hybridization?

Answer 8

It is the crossing of two true-breeding varieties.

Question 9

List the three generations involved in true-breeding and their names

Answer 9

The P generation are the true breeding parents
The F1 geenration are the first filial generation (filia means son in latin). They are the hybrid offspring of P-gen
The F2 generation are the second filial generation, produced by allowing F1 to self-pollinate or cross-pollinating them with other F1 hybrids

Question 10

Explain Mendel’s experiment to find what traits appear in F2 gen when F1 hybrids cross or self pollinate, and his conclusion

Answer 10

Mendel crossed two true-breeding vareities (purple and white flowers) and the F1 gen were all purple flowers. After the F1 gen self or cross pollinated, the F2 offspring had a ratio of 3:1 purple to white results.

Question 11

what is an allele? What causes their existence?

Answer 11

It is an alternative version of a gene. It is caused by the fact that each somatic cell has two copies of each chromosomes and therefore two copies of each gene which may be identical or different alleles.

Question 12

What accounts for variation in inherited characters?

Answer 12

Alternative versions of genes, or alleles

Question 13

How many copies of each gene does an organism inherit ?

Answer 13

For each character, an organism inherits two copies, one from each parent

Question 14

Which allele determines the organism’s character if two alleles at a locus differ? In Mendel’s experiment, which one would this be?

Answer 14

the dominant allele, the purple colour

Question 15

What is a recessive allele?

Answer 15

It is the vairation that does not appear in a phenotype if a dominant allele is present

Question 16

What is the law of segregation?

Answer 16

Two alleles for a heritable character segregate during gamete formation and end up in different gametes.

Question 17

What is meant by segregate?

Answer 17

Seperate from each other

Question 18

Explain the variation in alleles of the gametes if an orgnaism is true-breeding for a character; if it is an F1 hybrid

Answer 18

If it is true-breeding, then the same allele for that character is present in all of its gametes
If it is a hybrid, 50% of gametes receive dmoinant allele, 50% receive recessive

Question 19

What is a Punnett square?

Answer 19

a device that predicts the allele composition of offspring. A capital letter is sued for dominant alleles and small letters for recessive

Question 20

What is meant when a character is homozygous?

Answer 20

The organism has identical alleles for that character

Question 21

What is meant when a character is heterozygous?

Answer 21

the organism has different alleles for that character

Question 22

What is a phenotype? What is a genotype? Give an example of each?

Answer 22

A phenotype is an organism’s appearance or observable traits. In F2 generation, the phenotype would appear to have the 3:1 ratio (purple to white)
A genotype is an organism’s genetic makeup. In F2 generation, the genotype would appear to have the 1:2:1 ratio (dominant homozygous to heterozygous to recessive homozygous)

Question 23

What is a testcross; explain how it is performed

Answer 23

It is a test to find the genotype of a mystery organism by breeding it with a recessive homozygote

Question 24

What are monohybrids?

Answer 24

A hybrid that is heterozygous for the one aprticular character that is followed in the testcross

Question 25

Monohybrid cross

Answer 25

A cross between two monohybrids

Question 26

What is a dihybrid

Answer 26

A hybrid that is heterozygouys for the two characters being followed in the cross

Question 27

Dihybrid cross

Answer 27

Cross between two dihybrids

Question 28

State the law of independent assortment

Answer 28

Each pair of alleles segregate independently during gamete formation

Question 29

Explain the dihybrid cross Mendel performed, and the phenotypic ratio of the offspring of the F2 gen. Why is this the ratio instead of the 3:1 just as in a monohybrid cross?

Answer 29

He crossed YR, Yr, yR, and yr sperms with eggs of the same alleles. The phenotypic ratio he got every time was 9:3:3:1 (YYRR to

Question 30

State the multiplication rule

Answer 30

To determine a probability of two events happening simultanetously, multiply the probability of one event by the probability of the other

Question 31

What is the only condition needed for the law of independent assortment to apply?

Answer 31

The genes or allele pairs need to be located on different chroms

Question 32

Give an example of the multiplication rule in genetics

Answer 32

Each hetrozygous plant has 1/2 chance of carrying the dominant allele (non-wrinkled) and 1/2 chance of recessive allele (wrinkled). The probability of zygote to have both dominant (RR) is 1/2 * 1/2 or 1/4

Question 33

What is the addition rule?

Answer 33

The probability that one of two independent events will occur is calculated by adding their individual probabilities.

Question 34

What is complete dominance?

Answer 34

Form of dominance where the dominant allele is seen in phenotype while recessive allele isn’t

Question 35

What is incomplete dominance?

Answer 35

Form of intermediate dominance in which resulting phenotype is a combination of phenotypes of both parental alleles

Question 36

What is codominance?

Answer 36

When both alleles affect phenotype in separate distinguishable ways

Question 37

What does the observed dominant/recessive relationship of alleles depend on for any character?

Answer 37

On the level that we examine the phenotype: organismal, biochemical, etc

Question 38

Define pleiotropy

Answer 38

The property of having multiple phenotypic effects

Question 39

Why does Mendelian inheritance not portray how genes really affect phenotypes?

Answer 39

Because most genes have the pleiotropy property

Question 40

What is epistatis? Explain how it is applied to Labrador dogs

Answer 40

when the phenotypic expression of a gene at one locus alters that of a gene at a different locus

Question 41

What are quantitative characters? What does this variation indicate?

Answer 41

They are characters that vary in the population in gradiations. An example would be human skin. This variation indicate phenoytpic inheritance, the effect of two or more genes on a single character

Question 42

What do scientists mean when they refer to certain characters as multifactorial?

Answer 42

They mean that many factors including genetic and environmental, influence the phenotype