Today- Criss Cross Applesauce worksheetTomorrow:Human Genome notes

Chapter 14

What is this?

Pedigree = Family Tree

Squares represent males

Circles represent females

Shaded shapes represent the presence of a trait

Pedigree cont.

Horizontal lines show a marriage.

Vertical lines show a child. Brackets show a group of children.

Start with the bottom and move upward when making a pedigree. It makes it easier to space shapes.

Reading a Pedigree

What is the gender of X?

How are Tom and Kenzie related?

How are Katie and Mary related?

Who is married to Nancy?

Practice

What do you notice about the trait?

What do you notice about the trait?

What do you notice about the trait?

Dominant / Recessive Traits

The Principle of Dominance states that some genes are dominant while others are recessive.Dominant = strong, overpowering (A)Recessive = weak, overpowered (a)

Assume word problems involve dominant / recessive relationship unless otherwise stated.

Other Genetic Traits

Incomplete dominance = blending Sickle cell anemia;

“spiderpig”

Codominance = more than one dominant allele Blood type

Multiple alleles = more than one allele Rabbit fur color; blood type

Polygenic traits = several genes Skin color

Gene linkage = genes are close to each other Freckles & red hair

(“Gingers”)

Basic Blood Types

Blood Type

Allele Genotypes

A IA IAIA or IAi

B IB IBIB or IBi

AB IA and IB IAIB

O i ii

Blood Type cont.

Blood type (A, B, AB, O) is actually the phenotype.

Blood can also be positive or negative, but that is based on a clotting factor.

Since type O is recessive, people with this blood type can ONLY RECEIVE type O. However, they can donate to anyone.

Since type AB is codominant, people with this blood type can RECEIVE ANY blood type. However, they can DONATE ONLY to people with type AB blood.

Solve blood type problems with Punnett Squares.

Blood Type Problem #1

Katie has type O blood. She has a child with a man who is heterozygous for type B blood. What is the probability the child is type O? Type B?

Answer #1

ii x IBi

50% type O (ii) 50% type B (IBi)

Blood Type Problem #2

Kenzie has type A blood. If we know that her mother is type O, what is the blood type of her father?

Answer #2

Kenzie is type A, so her genotype must be either IAIA or IAi. Since her mother is type O, which is recessive, we know that Kenzie’s genotype is IAi.

Kenzie must have received the IA allele from her father, which means that he has AT LEAST ONE IA allele. Which blood types have this allele?

Type A or Type AB

Human Chromosomes

Humans have 23 pair of chromosomesChromosomes 1-22 are called autosomes.

You have two copies of each autosome in your diploid cells.

Chromosome pair 23 are sex chromosomes. There are two alleles, X and Y. Usually XY = male and XX = female.

Read the numbers and/or letters

X-Linked Traits

X-Linked traits are usually recessive and are carried ONLY on the X chromosome.

Affect males more often than femalesWhy?

Examples: colorblindness, hemophilia

X-Linked Colorblindness

Karyotypes

A Karyotype is an enlarged picture showing chromosomes.

Karyotypes cont.

How are they used?Can identify some problems in fetuses. For

example, normal karyotypes have two copies of each chromosomes. Monosomies (1 copy) and trisomies (3 copies) can cause a disorder.

Can identify the genetic gender by looking at the X and Y chromosomes.

What do you know about this person based on their karyotype?

Chromosomal Disorders Everyone needs at least one X

chromosome. Since females have two copies, sometimes one copy is turned off in part of the body while the other is turned off somewhere else. This X-Chromosome Inactivation causes different phenotypes in different parts of the body. Example: multicolored cats

Sometimes the body misreads chromosomes and produces a different phenotype. Example: pseudohermaphrodites

Chromosomal Disorders cont.

In normal meiosis, gametes (sex cells) divide chromosomes equally. However, sometimes chromosomes are divided up unequally. This is called Nondisjunction and causes resulting offspring to have too many or too few chromosomes. Examples: Down Syndrome

Sex Chromosome Disorders are caused by nondisjunction of the sex chromosomes. Sometimes this can affect fertility among other things. Examples: Klinefelter’s Syndrome, Turner

Syndrome, Jacob’s Syndrome

Application of Human Genetics

The Human Genome Project is trying to identify the location of all genes in the human genome. Genome: entire sequence of genes

Since everyone’s DNA is unique (except for identical twins etc), scientists can now use DNA Fingerprinting to identify individuals.

Gene therapy tries to add, remove, or modify genes from a person’s genome. In some cases this creates a temporary cure, but it is still a highly experimental field of research.