Ch 13

Autosomal Inheritance

Patterns of inheritance not on a sex chromosome

• “standard” patterns of inheritance

Gene

Hereditary factor that influences particular trait

Allele

Particular form of a gene

Chromosmal syndrome where males taller than average

XYY syndrome

people with a Y chromosome are externally male like no matter how many X chromosome they have (T/F)

True

Individuals with normal set of chromosomes

Euploids

When a segment is deleted from one chromosome of homologous pair an inserted into other during crossing over in meiosis what error is ms likely to happen

Duplication deletion or inversion

Duplication

Barr body is a condensation process of the X chromosome t or f

True

Whats the barr body process similar to

Condensed state of chromosomes during cell division

What is the main purpose of performing the reciprocal cross?

A) To determine whether the trait follows Mendel’s law of independent assortment

B) To test if the trait is influenced by sex-linked inheritance or maternal factors

C) To confirm that the trait is dominant

D) To identify whether crossing over occurred during meiosis

B) To test if the trait is influenced by sex-linked inheritance or maternal factors

When is a Reciprocal Cross NOT Useful?

Reciprocal crosses will give the same offspring ratios regardless of parental sex when:

A) The trait is X-linked

B) The trait is Y-linked

C) The trait is autosomal

D) Cytoplasmic inheritance influences the trait

C) The trait is autosomal

2 alleles in a diploid may be the same or different (T/f)

True

Nondisjunction in Meiosis I

Nondisjunction during meiosis I results in which of the following gamete outcomes?

A) Half normal, half abnormal gametes

B) All gametes abnormal (2 with n + 1, 2 with n – 1)

C) Only one abnormal gamete

D) No change in chromosome number

B) All gametes abnormal (2 with n + 1, 2 with n – 1)

If nondisjunction occurs during meiosis II, how many gametes will be normal?

A) 0

B) 1

C) 2

D) 4

C) 2

A reciprocal cross gives different offspring ratios when male and female parents are swapped. What does this imply?

A) The trait is polygenic

B) The trait is sex-linked or maternally inherited

C) The trait is autosomal

D) The trait follows independent assortment

B) The trait is sex-linked or maternally inherited

Genotype

Listing of alleles of particular genes in an individual

Phenotype

Individual’s observable traits

In diploids, genotype lists 1 alleles of each gene (t/f)

False-lists 2 alleles of each gene for diploids

For haploids, it lists 1 alleles of each gene

Dominant allele

Allele taht produces its phenotype in heterozygous and homozygous genotypes

Recessive allele

Allele that produces its phenotype phenotype only in homozygous genotypes

Dominant alleles or recessive alleles doesnt imply high or low frequency/fitness (t/f)

True

Dominant allele phenotype recedes or disappears in heterozygous individuals (TF)

False - recessive alleles does phenotype

Pure line

Individuals of same phenotype that when crossed always produce offspring with same phenotype

Pure line individuals are heterozygouse for the gene in question (T/F)

False - homozygous

Hybrid

Offspring from crosses between homozygous parents with different genotypes

Hybrids are heterozygous (T/f)

True

Reciprocal cross

A cross in which phenotype of male and female are reversed compared with a prior cross

Used to test if sex of parent influences transmission of trait

Reciprocal cross

Testcross

Cross of homozygous recessiveindividual and an individual with the dominant phenotype but unknown genotype

Used to determine whether a parent with a dominant phenotype is homozygous or heterozygous

Test cross

Linked genes

Genes near each other on the same chromosome

Principle of independent assortmen

Describes how different genes independently separate from one another when reproductive cells develop

Who first observed principle of independent assortment

Gregory mendel

Thomas Hunt crossed which species phenotypes and genotypes

Normal red eyes and normal wings flys (pr+pr+vg+vg+)

+

Recessive purple eyes with.vestigial wings (prprvgvg)

Thomas Hunt Findings

pr and vg are linked genes due to chromosome recombination

Genes on separate chromosomes can be considered linked genes (T/F)

False-are never linked

All genes on the same chromosome are linked (T/ F)

False - genes that are farther are more likely to be separated due to homologous recombination

if parent one is homozygous for dominant allele and parent 2 is homozygous for recessive allele what is F1 generation?

all will be heterozygous dominant

filial generation

first generation resulting from crossing 2 parental lines

referred to as F1 generation

ffirst generation

genetic recombination

2 homologous chromosomes exchange segments with each other by crossing over during meiosis

what affects the likelihood of genes being more inherited together?

their distance from each other

calculated to determine the distance between 2 genes on chromosome

recombination frequency

recombination frequency definition

percentage of testcross progeny that are recombinants

color of chromosome segments with wild type allele

red

color of chromosome or segments with mutant alleles are

blue

in order to generate recombinant phenotypes, parental chromosomes are segregated (T/F)

false - generated by crossing-over between 2 linked genes

(parental phenotypes in testcross progeny are generated by segregation of parental chromosome)

how many types of gametes are produced in meiosis for F female dihybrid parent

4 -

Meiosis in the male testcross parent produces 4 types of gamete (T/F)

false - only 1 type prvg

no crossing over = parental / crossing over = recombinant T/F

true

recombination frequency formula

(number of recombinants/total number gametes ) x 100

defining characteristic of unlinked loci

frequency of approx. 50% recombination

high recombination frequency = more likely linked genes (T/F)

falese it means genes more likely farther from each other / unlinked

recombination frequency can only be measured among progeny of homozygous (T/F)

false - heteroygous only (ex: dihybrids)

cross overs between 2 genes that are close together are not common and very rare (T/F)

true

recombination frequencies can be used to make

linkage map

linkage map of chromosomes

shows relative locations of genes

mu and cM are units for ______ and equivalent to recomnbination frequency of _____%

map unit

centimorgan

1%

karyotype vs idiogram

karyotype - actual chromosome

idiogram - diagram of those chromosomes

genes assort independently if no linkage is detected between them (T/F)

true

genes that are far apart on the same chromosome can still be linked as long as they’re linked to another gene located between them (ex: gene a —-b——c)

since a—-b

and b——c

so a——c

sex-linked genes

genes located on sex chromosines and inherited differently in males and females

autosomes

genes located on chromosomes other than sex chromosomes

autosomes have different patterns of inheritance in males and females (T/F))

False - same patters of inheritance in both sexes

which chromosomes are autosomes

chromosomes 1-22

homogametic sex

XX females

heterogametic sex

XY - males

some insects have XX females and XO males (T/F)

true

birds, butterflies, and some reptile sex chromomes

males = ZZ

females = ZW

bees and wasps sex chromosomes

sex is determined whether they’re haploid or diploid

what gene does human sex determination depend on and on what chromosome

SRY gene - sex determining region in Y gene

SRY gene function

determine human sex

initiate development of testes

crisscross inherihance

x - linked gene (white - eye allele) from male parent to female child to male grandchild

inheritance of sex-linked genes can be determined by reconstructing genotypes snd phenotypes of past generations using a chart called

pedigree

X-linked recessive traits appear more frequently among which gender and why

males bc they net receive only one copy of allele on X chromosome

how can females reflect x-linked gene

must receive 2 copies of recessive allele, one from each parent

example of X-linked trait

hemophilia

• queen victoria was a heterozygous carrier for recessive hemophilia allele

why do x-linked traits alternate from generation to generation in males?

bc x chromosome received by a male always comes from his mother in this case mother who’s a carrier of x-linked trait

dosage compensation mechanism

inactivates one of the 2 X chromosomes in most body cells of females

done to determine if gender influenced inheritance

reciprocal cross

when is one of the 2 x chromosome randomly inactivated

early during embryonic development

when one of the 2 x chromosome is inactivated, that same X is inactivated in ALL descendants of the cell T/F

true

calico cat x chromosome inactivation

calico cats are patchy because each skin cell randomly uses 1 X (other one is turned off) showing either black or orange

White patches in calico cats are also affected by x chromosome inactivation (T/F)

false - caused by autosomal gene that blocks pigment deposition in fur

chromosomal mutations

changes in chromosome structure of chromosome number

when do changes in chromosome structure occur

when DNA breaks and broken fragments may be lost or attach to same or different chromosomes

deletion

segment is lost from chromosome

duplication

a segment is broke from one chromosome and inserted into its homolog, adding to the segments already there

translocation

a segment is attached to a different, nonhomologous chromosome

inversion

a segment reattaches to the same chromosome but in reversed orientation - the order of the genes is reversed

in translocation a segment is attached to the same homologous chromosome (T/F)

false - different, nonhomologous chromosome

when can chromosome deletion cause severe problems

if missing segment is essential for normal development

(Ex: cri-duchat syndrome - C5 deletion intellectual disability and physical abnormalities)

all chromosome duplication are detrimental (T/F)

false - most duplications are likely detrimental BUT some have been important source of evolutionary change

Duplication pros

one copy can mutate into new forms without seriously affecting the basic functions of the organism

when can duplication occur

during uneven crossing over in meiosis

most common type of chromosomal mutation in many cancers

translocation

translocation example

chronic myelogenous leukemia - philadelphia chromosome (altered C22) arises when regulatory ABL gene from C9 fuses with BCR gene on C22

inversions have same effect as translocations (T/F)

true

in Inversion, Genes may be broken internally with loss of function or transferred intact to new location within same chromosome (T/F)

true

2 changes in chromosome structure that have been important factors in evolution

inversion and translocation