250 Quiz 1

mutations within introns can often prevent

normal processing of the primary RNA transcript

n =

number chromosomes in genome

monohybrid cross tests how many traits

one

haplosufficient

one gene copy has enough function to produce wild-type phenotype (*null mutant allele is recessive*)

law of equal segregation

pair of inheritance unit factors (alleles) segregate with equal probability during myosis, the formation of gametes

autosomal recessive pattern

parents of progeny usually unaffected

zygote

product of two gametes (diploid)

how to demonstrate single-gene inheritancve of sterile mutants

propagate as heterozygote and self to look for 25% (if sterile recessive. sterile dominant is dead end, but can be asexually propagated in plants/fungi)

person of interest in pedigree analysis

propositus

at the molecular level, the primary phenotype of a gene is _______ produced

protein

exons

protein-coding regions of the gene

autosomal dominant disorder examples

pseudoachondroplasia, huntington disease, polydactyl (extra digits), piebald spotting

autosomal polymorphism pattern

recessive allele more common

x-linked recessive disorder examples

red-green colorblindness, hemophilia

leaky mutations

reduced enzyme function

what is development?

single fertilized cell --> mature adult

model organism traits

small size, small genome, short generation time, many offspring

law of equal segregation is based on

chromosomal segregations in meiosis

genotype

collection of all alleles

test cross

cross A/- with recessive "tester" (a/a). If 1:1, it's A/a, If all show dominant, it's AA. (you can also self the unknown)

to check for single-mutant alleles, researchers...

cross mutant with wild-type and look for 3:1 ratio if recessive mutation or 1:1 if dominant mutation

dominant vs. recessive can only be determined after

cross to get heterozygouse

which one increases genetic diversity?

cross-pollination (not self)

each gamete contains unique genetic info due to _________________

crossing-over in S phase

autosomal recessive disorder examples

cystic fibrosis, PKU

at the molecular level, alleles of the same gene differ at

only one or several nucleotides (mutations can be change, insertion, deletion)

progenitor

original cell; ancestor

autosomes

"normal" (nonsex) chromosomes

F2 name

"second filial generation"

genes in differential sex regions show

"sex linkage" inheritance patterns

meiosis

***my image***

autosomal dominant pattern

-phenotype usually appears in every generation (most affected people are heterozygotes)

single-gene inheritance ratios

1:1, 3:1, 1:2:1

3:1 phenotypic ratio in F2 of heterozygous F1 cross (monohybrid cross) is underlying...

1:2:1 (Y/Y : Y/y : yy)

homologous chromosomes, a.k.a. homologs

2 members of a chromosome pair

meiosis brief summary

2 sex cell divisions and 2 nuclear divisions (meiosis), but chromosome replication only occurs the first time, forming haploids

pseudoautosomal regions 1 and 2

2 short homologous regions at each end of human X and Y chromosomes (one or both undergoes crossing over during meiosis)

mitosis equations (for both diploid and haploid cells)

2n --> 2n + 2n, OR n --> n + n

meiosis equation

2n --> n + n + n + n (diploid to haploid)

ratio when two heterozygotes cross

3:1

how many chromosomes do humans have

46 (22 homologous autosomes and 2 sex chromosomes)

what percentage of the cell cycle is mitosis

5-10% (the rest is interphase during which DNA is replicated!)

PKU caused by

PAH deficiency in metabolic pathway (can't metabolize phenylalanine)

example of monohybrid cross

Y/y x Y/y

null mutations are located on

active site, promoter, or between intron and exon (last option could impair intron removal)

x-linked dominant pattern

affected males pass condition to all daughters but no sons ALSO affected heterozygous females x unaffected males pass condition to half sons and daughters

pure line

all offspring have identical phenotypes

genes come in two forms called

alleles

"molecular base of gene variant" is

base pair difference

autosomal polymorphism exaamples

dimorphisms brown vs. blue eyes, pigmented vs. blond hair

2n denotes a

diploid cell

leaky mutations might be located on

end region of active site

homogametic

females

zygote

fertilized egg

another name for progeny gen.

first filial generation (F1)

recessiveness is observed in

functionally haplosufficient genes; wild type is dominant

silent mutations

functionally wild-type

gp denotes

gametophyte (small structure of haploid cells that will produce gametes)

hemizygotes

genes in differential regions of sex chromosomes

are gametes haploid or diploid?

haploid

n denotes a

haploid cell

mutated allele is dominant in

haploinsufficient genes

dioecious plants

have sexual dimorphism

monohybrid explanation

heterozygote for one gene

inbreeding increases the chance that _______ will mate

heterozygous

monohybrid

heterozygous for one trait

x-linked dominant disorder examples

hypophosphatemia (a type of vitamin D-resistant rickets)

best way to study forward genetics?

identify mutant and compare to wild-type phenotype

allele phenotype won't be expressed if...

in intron region

law of equal segregation (book explanation)

in meiosis, members of gene pair separate equally into product cells (gametes, e.g. sperm and egg) so a single gamete contains only one allele

name of Mendel's first law

law of equal segregation

heterogametic

males

________ divide to produce sex cells (gametes), such as sperm and egg

meiocytes

sexual nuclear division

meiosis

equal segregation is only detectable at the genetic level in...

meiosis of heterozygote (1/2 Y and 1/2 y gametes)

somatic cell nuclear division

mitosis

somatic cell division stages

mitosis --> G1 --> S (DNA synthesis) --> G2

x-linked recessive pattern

more common in males than females because females need both sex alleles to be recessive, whereas males need only one ALSO no offspring of affected males show phenotype, but all daughters are carriers

null alleles

mutant alleles completely causing proteins to lack original function

silent mutations might be located on

non-active site region of exon

To check genotype of phenotype, use a

test cross

what happens to gametes at fertilization

they randomly fuse

dihybrid

two traits, both hybrid (e.g. XxYy)

forward genetics

understanding molecular mechanism for phenotype and phenotypic differences

in haploids, assigning dominance is...

usually not possible

haploinsufficient

wild-type allele can't provide enough product for normal function, so null mutant allele is dominant

does the law of segregation also apply to DNA sequences along the chromosome?

yes