Simple Inheritance Patterns

Question 1

do most mutations in your genome affect phenotype?

Answer 1

no, they are not “functional” mutations

Question 2

describe functional mutations; how are they transmitted?

Answer 2

affect phenotype; can only be transmitted to the next generation if they are in the “germline” cells of the organism

Question 3

describe the “germ line”

Answer 3

lineage of cells set aside during development to differentiate into gametes in the adult

Question 4

when is the germ line established?

Answer 4

when the embryo is patterned during development, like any other cell type

Question 5

rest of the cells (besides germ line cells)

Answer 5

somatic cells

Question 6

mutations that occur in the germline during meiosis give rise to…

Answer 6

mutant gametes

Question 7

if the mutation in the germline is functional, what does the gamete give rise to?

Answer 7

a new “mutant” individual with a new phenotype after fertilization and development

Question 8

when do mutations occur during mitosis?

Answer 8

any point in an individual’s life

Question 9

consequence of mutations that occur in a differentiated cell that is no longer dividing (or dividing very little)

Answer 9

won’t alter an organisms phenotype, even if they are “functional mutations”

Question 10

consequence of mutations that occur during mitosis in a cell that keeps dividing

Answer 10

will create a population of cells with a different “genotype” than the rest of the organism

Question 11

describe “genetic mosaics”

Answer 11

individuals in which a subset of cells have acquired new mutations (we are all one), a lot of the mutations are not “functional” and don’t affect phenotype

Question 12

what happens if a functional mutation occurs during mitosis early in development?

Answer 12

may give rise to a genetic mosaic with a mosaic phenotype

Question 13

if a functional mutations occurs during the first cell division of a zygote, what is the result?

Answer 13

the resulting individual’s cells will carry the mutation and display the phenotype

Question 14

if a functional mutation affects the germline cells, what is the result?

Answer 14

the mutation can get passed on to the next generation

Question 15

results of functional mutations in the “cell cycle checkpoint genes” of dividing cells (skin cells, breast tissue, lung tissue)

Answer 15

can lead to cancer (a type of genetic mosaicism)

Question 16

if your parents have cancer, you won’t automatically inherit their cancer. why?

Answer 16

the series of mutational “hits” that ultimately cause most cancers are in somatic cells (not germline)

Question 17

why then does cancer have a heritable aspect?

Answer 17

you do inherit any mutational “hits” transmitted from your parents in their germline cells that make cancer more likely

Question 18

are phenotypes caused by heritable functional mutations always transmitted perfectly to offspring? why?

Answer 18

no, because of sexual reproduction

Question 19

describe the blending hypothesis

Answer 19

old idea that traits simply mix like paint colors to give a variety of intermediate forms

Question 20

describe the particulate hypothesis

Answer 20

traits transmitted as distinct units

Question 21

Mendel’s 4 part model for particulate inheritance

Answer 21

1) different versions of the same gene, called alleles account for differences in a trait between individuals
2) for each gene an individual inherits two alleles, one from each parent
3) if the two alleles an individual has are different, one will determine the appearance, it is “dominant”
4) an individual only passes on one allele to its offspring, which allele a particular offspring gets is random (law of random segregation)

Question 22

“dominant”/“recessive” alleles

Answer 22

rare, not the best way to describe it

Question 23

Mendel’s main insight

Answer 23

explained the inheritance patterns he saw over generations as ratios/percentages

Question 24

no matter how many alleles Mendel looked at at once, how did they behave?

Answer 24

the behaved statistically independently; they were unlinked and assorted independently

Question 25

define trait/character

Answer 25

any aspect of the form or function of an organism (may or may not be determined by genes)

Question 26

define phenotype, give an example

Answer 26

a particular measurable “state” for a character; character is hair color, phenotype is black hair color

Question 27

what is phenotype determined by

Answer 27

may or may not be determined by genes (could be from the environment) but for this class, phenotype is determined by genes

Question 28

define wild type phenotype

Answer 28

the most common likely original and ancestral phenotype during a given time frame

Question 29

define gene

Answer 29

transcribed DNA sequences and their associated CREs that contribute to the form and function of an organism (analogous to trait or character)

Question 30

define allele

Answer 30

a particular version of a gene, with or without mutations (analogous to phenotype)

Question 31

define genotype (specific)

Answer 31

the two alleles of a gene present in an individual

Question 32

define genotype (general)

Answer 32

all the alleles of all genes in an individual

Question 33

what is the dominant allele (simple Mendelian gene)

Answer 33

the functional, wild type allele

Question 34

what is the recessive allele (for simple Mendelian genes)

Answer 34

the “broken” allele (caused by a loaf of function mutation)

Question 35

when does complete mendelian dominance of one allele work?

Answer 35

ONLY works if one good copy is enough to create the dominant phenotype (half dose of a gene’s product is as good as a full dose)

Question 36

many genetic disease/ disorders that behave like simple Mendelian traits are mutations in what kind of genes?

Answer 36

tissue-specific effector genes

Question 37

describe the term “carriers”

Answer 37

heterozygous for the dominant, functional wildtype allele and the broken, recessive allele

Question 38

why is incest a bad idea?

Answer 38

we are all carriers of pathological and/or deadly recessive mutation alleles

Question 39

basis of Mendel’s “law of random segregation”?

Answer 39

due to independent assortment of homologous chromosomes during meiosis

Question 40

genes are on _____, alleles are on ______

Answer 40

chromosomes; homologous chromosomes

Question 41

what does crossing over during meiosis ensure?

Answer 41

independent assortment of genes, even when they are on the same chromosome