Transcript Chapter 11 ppt student notes pt 1

C HAPTER 11:
C HROMOSOMES
I NHERITANCE
AND
H UMAN
H UMAN C HROMOSOMES

Most animals have a _________number of
chromosomes: _____

Humans have ____ pairs of chromosomes

All (except one) of those pairs are called
_______________


Same length, shape, and centromere
location

Humans have ___
______ _______________ are the last pair
S EX C HROMOSOMES

Sex chromosomes determine ________

Males : ___

Females: ____

X and Y chromosomes differ in length,
shape, and the genes they carry
___ __________

Each egg contains 22 autosomes + an X
chromosome

Sperm will contain 22 autosomes + either
an X chromosome OR a Y chromosome

Egg and sperm combine  either XX
(female) or XY (male)

Reference figure 11.2, pg. 170
S EX D ETERMINATION :
Y C HROMOSOME

Fewer than two dozen genes identified

The Y chromosomes carries the ____ ______


Master gene for male sex determination
Expression of SRY gene triggers formation of
________ , which are the primary male sex
organs (or gonads)

These secrete ________________, which
is responsible for the male secondary sex
traits
S EX D ETERMINATION
Reference
figure 11.2

Absence of the male-determining SRY gene
in females results in the formation of ovaries

Mutations in the SRY gene causes
individuals who are XY to develop as
females

The X chromosome codes for sexual traits
but ALSO carries many genes for nonsexual
traits

X chromosome carries over ______ genes

Males only have one copy of these genes
K ARYOTYPING

A _____________ is a diagnostic tool that
is a preparation of an individual’s
metaphase chromosomes

Mitosis is arrested in _________

Chromosomes are photographed, and
then cut out and arranged by pairs
according to size, shape, and length

Array can be compared to a normal
standard and analyzed for extra or missing
chromosomes
K ARYOTYPING
Figure 11.3, pg. 171
H UMAN
GENETIC ANALYSIS

Humans are difficult to study genetically due to
long life spans (compared to a fruit fly or a
garden pea) and small families

Data on human inheritance is displayed in
_________________

A pedigree is a chart that shows genetic
connections among individuals

Analysis of family pedigrees provides data on
inheritance patterns through several
generations
P EDIGREES

Knowledge of ______________ and
________________________________ is
used in analysis of pedigrees to yield clues
to a trait’s genetic basis

Conclusions most accurate when drawn
from large number of pedigrees

Can be used to predict the risk of disease
in future offspring in a family (genetic
counseling)
P EDIGREES

Uses standardized symbols:

Squares = ________ , Circles = ______

Shaded squares/circles = those who carry
trait of interest

Horizontal line between male/female =
__________________

Number generations from oldest (top) to
youngest (bottom) with Roman numerals

Number individuals within a generation from
oldest (left) to youngest (right) with Arabic
numerals
E XAMPLE P EDIGREE
A
PEDIGREE FOR POLYDACTYLY
Polydactyly:
An unusual
number of
fingers of
toes
Figure 11.17,
pg. 180
G ENETIC
DEVIATIONS
Genetic ________________ is a term applied to a
genetic condition that is a deviation for the usual (or
average) and is not life-threatening
 Rare or less common version of a trait
 Genetic ______________ is used to describe conditions
that cause medical problems
 ______________ is a recognized set of symptoms that
characterize an abnormality or disorder
 A disease is an illness caused by infection or
environmental factors
 A genetic _____________ is a term used only when
factors alter previously workable genes in a way that
disrupts body functions

A UTOSOMAL I NHERITANCE PATTERNS

Some alleles on autosomes are
inherited in simple Mendelian patterns

Certain mutated forms of alleles give
rise to genetic abnormalities or
genetic disorders
______________________
Figure 11.4a,
pg. 172
A UTOSOMAL D OMINANT
I NHERITANCE




The dominant allele is nearly always
expressed, even in heterozygotes
If one parent is heterozygous and the other
homozygous recessive, there is a 50%
chance that their child will be heterozygous
If the gene (and its resulting disorder)
reduces the chance of surviving or
reproducing, its frequency should decrease
However, it may not due to:
E XAMPLES :
A UTOSOMAL D OMINANT
Acondroplasia (dwarfism)
 A benign abnormality that does not affect
persons’ ability to reproduce
 Adults have abnormally short arms and
legs
 Huntington disease
 A serious degeneration of the nervous
system with an onset from age 40 onwards
 At this point, the gene has typically been
passed from parent to offspring
unknowingly

____________________
A UTOSOMAL RECESSIVE
INHERITANCE

Either parent can carry the recessive allele on
an autosome

Heterozygotes are symptom-free;
homozygotes are affected

Two heterozygous parents have a 50% chance
of producing heterozygous children and a 25
percent chance of producing a homozygousrecessive child

When both parents are homozygous, all
children can be affected
E XAMPLE :
A UTOSOMAL R ECESSIVE

Galactosemia: the inability to metabolize
lactose

A single gene mutation prevents the
manufacture of an enzyme needed in the
conversion pathway

Lactose  galactose  glucose-6phosphate, which can be converted to
glycogen or enter glycolysis
N UEROBIOLOGICAL DISORDERS

Nuerobiological disoders (NBDs) include:

Changes in genes contribute to the abnormal
biochemistry in NBDs

Most NBDs involve multiple genes and
environment factors – not just a single allele

Some mutated alleles are linked to these
disorders and can predispose a person
H UTCHINSON -G ILFORD
P ROGERIA SYNDROME

Premature aging is caused by a mutated
allele

In one of 8 million newborn humans, a
mutated gene will cause accelerated aging

Observable symptoms arise by age two

Their skin thins, skeletal muscles weaken,
bone growth ceases, hair loss occurs, and
they “look old”

Most progeriacs expect to die in their teens
______ I NHERITANCE PATTERNS

Certain dominant and recessive alleles on the
X chromosome are inherited in Mendelian
patterns

Approximately _________ of all genes are
located on the X chromosome

Mutated alleles on the X chromosome
contribute to more than 300 known genetic
disorders

Males can’t transmit X-linked alleles to sons:
X- LINKED
INHERITANCE

In X-linked recessive inheritance, the
mutated gene occurs only on the X
chromosome

Males are more often affected because a
single recessive allele on the X
chromosome cannot be masked by a
dominant gene on another chromosome

Heterozygous females are phenotypically
normal
X- LINKED
INHERITANCE
X- LINKED
INHERITANCE

A normal male mated with a female
heterozygote (or carrier):

Homozygous recessive female and a normal
male:
H EMOPHILIA
A

Hemophilia is a serious X-linked recessive
condition that prevents blood from clotting
properly

The blood cannot clot because the genes do
not code for the necessary clotting agent or
agents

Today, hemophilia affects about 1 in 7,500
people

This number may be increasing because
hemophilia is now treatable
R ED -G REEN C OLOR B LINDNESS

Color blindness is the inability to distinguish
colors

Mutated genes change the light-absorbing
capacity of sensory receptors in the eyes

Normal people can distinguish among 150 colors

People with red-green color blindness can only
see 25 colors (or fewer)

Males are 12 times more likely than women to
be affected by color blindness
D UCHENNE MUSCULAR DYSTROPHY

Duchenne Muscular Dystrophy (DMD) affects
about 1 in 3,500 boys

It’s characterized by a rapid degeneration of
muscles

A recessive allele encodes for dystrophin, a
structural protein in muscle fibers

Abnormal or absent dystrophin causes the
muscle degeneration