Chapter 12 - Mendels Expirements And Heredity

Question 1

What did Mendel discover before meiosis was understood?

Answer 1

The fundamental principles of inheritance

Question 2

Today we refer to what basic understandings of what genes are as…

Answer 2

Classical or Mendelian genetics

Question 3

What type of plants did mendel use mostly to study inheritance patterns?

Answer 3

Pea plants

Question 4

What did Mendel demonstrate in his studies of traits?

Answer 4

That traits are transmitted from parents to offspring independent of other traits and in dominant and recessive patterns as discrete units (factors, genes)

Question 5

What is blending inheritance?

Answer 5

A prevailing theory at the time of Mendel that inheritance involved blending of parental traits producing intermediate physical appearance in offspring

Question 6

What is continuous variation a result of?

Answer 6

The action of many genes that determine a characteristic (eg human height)

Question 7

What is discontinuous variation?

Answer 7

When traits are inherited as distinct classes like violet flowers vs white flowers (same characteristics but different traits)

Question 8

The parents crossed in generation one is called what?

Answer 8

The parental generation or P0

Question 9

The seeds produced by the parental generation were collected and grown the following season producing what? What happens with a seeding the following year after that?

Answer 9

The first filial generation or F1. Then allowing the F1 generation to self pollinate, collect and grow their seeds produces the F2 generation

Question 10

Mendel performed crosses on seven different characteristics each with 2 constraining traits. What did he find when a true breeding violet plant was crossed with a true breeding white plant in F1 and in F2?

Answer 10

In F1 he found that 100 percent of the plants had violet flowers (white flower trait had completely disappeared) but when F1 was self pollinated and produced F2 there was a ratio of 3:1 of violet to white plants respectively.

Question 11

What did Mendel call the traits that are unchanged in hybridizations and those that disappear?

Answer 11

Those that went unchanged were dominant traits, those that disappeared were called recessive traits

Question 12

How does the masking of the recessive traits work? What needs to happen for it to be expressed?

Answer 12

There needs to be 2 recessive factors that are paired. Otherwise it will be dominant that is expressed. (This includes 1 dominant and 1 recessive, and of course 2 dominant)

Question 13

Probability of 2 carriers of albinism having an albino child?

Answer 13

25%

Question 14

Where are genes?

Answer 14

On chromosomes

Question 15

Gene variants which exist at the same relative location on homologous chromosomes are called what?

Answer 15

Alleles

Question 16

More than 1 gene (a pair of alleles) may code for a single trait called…

Answer 16

Polygenic inheritance

Question 17

Observable traits expressed by an organism is called what? Vs what is an organisms underlying genetic makeup called?

Answer 17

Observable expressed traits are phenotypes while underlying genetic makeup is called a genotype

Question 18

Organisms that have two identical alleles for that gene on their homologous chromosomes are called what? What if they were different what would they be called?

Answer 18

Identical would be homozygous while different would be heterozygous

Question 19

Individuals that differ in only one characteristic that breed is called what?

Answer 19

Monohybrid cross

Question 20

How can a dominant expressing individuals genotype be determined?

Answer 20

Crossing it with a homozygous individual, if it is a dominant homozygous individual then it will produce all dominant trait offspring

Question 21

In rare cases heterozygous individuals appear to be intermediate between the two parents. What would that mean in snapdragons if there was a cross between homozygous parent with white flowers and homozygous with red flowers? What would they produce??

Answer 21

They would produce pink flowers, that is that the red flowers are incompletely dominant over allele for white flowers

Remember it is still NOT blending

Question 22

Both alleles for the same characteristics are expressed. What is this called?

Answer 22

Codominance

Question 23

In codomiance how is the MN blood groups shown in punnet square if they are heterozygotes, along with heterozygotes of ABO?

Answer 23

Heterozygotes of MN is expressed equally in both alleles as (LM, LN)

While heterozygotes for ABO is (IA, IB)

Question 24

The sex chromosomes are non homologues in who?

Answer 24

The males ( the Y has almost negligible length)

Question 25

The non sex chromosomes are called what?

Answer 25

Autosomes (1-22 pair in humans)

Question 26

When a gene is present on the X chromosome, but not on the Y chromosome it is called what?

Answer 26

X-linked

Question 27

What are males referred to in their sex chromosome since they have only one allele for x linked chromosomes?

Answer 27

Hemizygous

Question 28

What would happen to the offspring if a female is homozygous for a recessive x linked trait?

Answer 28

They will get it 100% of the times since their fathers Y chromosome does not have the loci for that allele

Question 29

Why can’t males be carriers for human sex linked disorders?

Answer 29

Because they only need to inherit one recessive mutant X Allele to be affected

-meanwhile females must inherit recessive X linked alleles from both parents

Question 30

Rare recessive lethal alleles exist where the homozygous genotypes are lethal and the heterozygotes are normal. What usually happens to the development in these individuals?

Answer 30

They fail to develop past fertilization, or die in utero (miscarriage)

Question 31

Rare dominant lethal alleles also exist where both homozygous and heterozygous individuals die, this allele can only be inherited if the lethality phenotype occurs when? What is the main example of this type of disease and when does onset occur?

Answer 31

Lethality phenotype occurs after reproductive age, it often seen in Huntington’s disease where heterozygous individuals will eventually develop the fatal disease, onset does not occur until age 40

There is a 50% chance they pass it to their offspring

Question 32

What did independent assortment look at?

Answer 32

When 2 different characteristics relate to each other

Question 33

The physical basis for the law of independant assortment lies when?

Answer 33

In meiosis 1 when different homologous pairs line up in random orientations on the metaphase plate

Question 34

What can violate the law of independent assortment?

Answer 34

Linked genes, that is genes in the same chromosome. Genes need to be in different chromosomes for it to work.

Question 35

How are genes located physically close to each other in the same chromosome likely to be inherited?

Answer 35

As a pair

Question 36

When genes act antagonistically to other genes it is called…

Answer 36

Epistasis

Question 37

Genes being masked are called what? While the genes doing the masking are called…

Answer 37

Masked genes are hypostatic genes, the genes that do the masking are called epistatic genes