11.1 BASIC PATTERNS OF HUMAN INHERITANCE

11.1 BASIC PATTERNS OF HUMAN INHERITANCE

WHAT YOU WILL LEARN-How to determine if an inherited trait is dom/rec-Examples of DOMINANT/RECESSIVE disorders-How a PEDIGREE shows a particular trait in families

MAIN IDEA

The inheritance of a trait is shown over several generations in a pedigree.

READING Q’s

REVIEW VOCAB: enzyme-PROTEIN that speeds up biological reactions

READING Q’s

IDENTIFY-CIRCLE the term that describes the genotype of a person who expresses a recessive trait

-homozygous: organism with 2 of the same alleles for a particlular trait

-DETERMINE the genotypes:recessive genetic disorderdominant genetic disorder

DD Dd dd

DD Dd dd

XX X

READING Q’s

EXPLAIN-Why do ganglioslides build up in the brain of people with Tay-Sachs disease?

-ENZYME missing that breaks down ganglioslides—fatty acids

READING Q’s

EXPLAIN-How scientist determine if achondroplasia developed from a new mutation

-achondroplasia is a dominant disorder: dwarfism-if BOTH parents are average height it dev from MUTATIONParents would be homozygous recessive so could only pass on a recessive allele—dominant allele would have to be a mutation

READING Q’s

EXPLAIN the purpose of a genetic pedigree-track a trait or disorder throughout several generations

DRAW the symbols used in a pedigree for:MALE= FEMALE=

READING Q’s

EVALUATE-Circle the carriers in the second generation

READING Q’s

CALCULATE-What percentage of the children in this family inherited Tay-Sachs disease?

-1/4=25%

READING Q’s

IDENTIFY-Do any grandchildren in this family have polydactyly?

-NO

READING Q’s

EXPLAIN-Why are recessive traits difficult to study?

-Not all people who carry the recessive allele have the trait-Don’t know if you are a carrier unless___

-1 parent shows the trait = homozygous recessive

-offspring shows trait = both parents carriers

GROUP WORK: APPLICATION NOTES

-As a group complete the guided note sheet using your knowledge from the reading.

REVIEW VOCAB

DEFINE: gene-segment of DNA on chromosomecarrier-heterozygous for a recessive disorder--Aa

RECESSIVE/DOMINANT GENETIC DISORDERS

COMPARE: RECESSIVE GENETIC DISORDERS

-only present if homozygous recessive-parents are carriers if don’t have disorder

DOMINANT GENETIC DISORDERS-present if have at least 1 dominant allele-must have a parent with the disorder

[mutations are exceptions]-don’t always appear until later in life


IDENTIFY: 1-four examples of recessive genetic disorders in humans1-CYSTIC FIBROSIS2-TAY-SACHS3-ALBINISM4-GALACTOSEMIA5-ALKOPTONURIA2-two examples of dominant genetic disorders in humans1-HUNTINGTON’S2-ACHONDROPLASIA


EXPLAIN why recessive disorders are more common than dominant disorders.-don’t always know there are carriers of disorder-parents may not know the disorder is in the family


IDENTIFY: the disease for each dominant/recessive disorders-caused by altered genes; results in lack of skin pigmentation

-ALBINISM-recessive

-characterized by body’s inability to tolerate galactose-GALATOSEMIA-recessive

-gene found on chromosome 15;characterized by lack of enzyme that breaks down fatty acids

-TAY SACHS-recessive


IDENTIFY: the disease for each dominant/recessive disorders-affects the nervous system; no treatment; breaks down part of brain

-HUNTINGTON’S-dominant

-affects mucus-producing glands, digestive enzymes, sweat glands

-CYCTIC FIBROSIS-recessive

-affects height and body size-ACHONDROPLASIA-dominant


-SHOW a cross between 2 carriers-what is the probability 2 carriers of cystic fibrosis will have a child w/CF?

F

FF

Ff

ff

Ff

f

F

f-25%


PREDICT: -can 2 normal height parents have a child w/achondroplasia?

a

aa aa

aa

aaa

a

a


PREDICT: -can 2 individuals w/achondroplasia have a child that is normal height?

A

AA Aa

aa

Aa

a

A

a

PEDIGREESSUMMARIZE: pedigree symbolsMALE

-square-FEMALE

-circle-AFFECTED MALE

-shaded square-AFFECTED FEMALE

-shaded circle-

CARRIER-half shaded symbol- / PARENTS--circle joined to square

PARENTS/OFFSPRING

-line down from parent/ circles/squares on second row-

PEDIGREE CHART

PEDIGREE CHART

GRANDPA X GRANDMA MOM X DAD GRAMPS X GRANNY

ANALYZING PEDIGREES

EVALUATE: the inheritance of achondroplasia shown in the pedigree

-parent w/ disorder-father

-#children with disorder-1 / 1st born son

-genotype of younger son-homozygous recessive / aa

ANALYZING PEDIGREESANALYZE and RESPOND: -RECALL if the trait is rec or dom based on the following information: -In the pedigree, individuals I-1 and I-2 are unaffected -- have affected childRECESSIVE DOMINANT-SPECIFIY if parents II-1 and II-2, who have an affected child, are carriers of that traitCARRIER NOT A CARRIER-TELL whether there is a dominant gene in the genotype of II-4NONE A LEAST ONE-Individual II-1is in generation 2 TRUE FALSE

X

X

X

X

ANALYZING PEDIGREES

THINK BACK and RESPOND: -A scientist uses a pedigree to study family historyTRUE FALSE-A pedigree traces the inheritance of a particular trait through only two generationsTRUE FALSE-In a pedigree, one who does not express the trait is represented by a darkened circle/squareTRUE FALSE-In a pedigree, a horizontal line between 2 symbols shows that these individuals are the parents of the offspringTRUE FALSE

X

X

X

X

MANY

ANALYZING PEDIGREES

DIAGRAM: Suppose both parents can roll their tongues but their son cannot.IDENTIFY this trait as: dominant recessiveDRAW a pedigree showing this trait LABEL each symbol with the appropriate genotype

What was the probability that they would have a non-tongue roller offspring? (hint: punnet square)

-both parents carry recessive gene-parent genotype Tt-son genotype tt

-probability of child tt= 25%

Connecting Pedigree Symbols

parents

offspring

EX- PEDIGREE CHART

Interpreting a Pedigree Chart1- Determine whether the trait/disorder is

dominant or recessive

-If the trait/disorder is dominant, one of the parents must have the disorder-If the trait/disorder is recessive, neither parent has to have the disorder because they can be heterozygous

• Dominant or Recessive?

PRACTICE: Interpreting

Answer

• Recessive

Dominant or Recessive?


Answer

Dominant

Interpreting a Pedigree Chart

2- Determine if the pedigree chart shows an autosomal or X-linked trait/disorder

-If most of the males in the pedigree are affected the trait/disorder is X-linked -If it is a 50/50 ratio between men and women the trait/disorder is autosomal.


Is it Autosomal or X-linked?

Answer

Autosomal

Summary

-Pedigrees are family trees that explain your genetic history.

-Pedigrees are used to find out the probability of a child having a trait/disorder in a particular family.

-To begin to interpret a pedigree-determine if the trait/disorder is:

1-dominant or recessive2-condition is autosomal or X-linked

PEDIGREE PRACTICE A

PEDIGREE PRACTICE B

PEDIGREE PRACTICE C

PEDIGREE PRACTICE D

INVESTIGATING HUMAN PEDIGREES

-USE the information provided in the transcript to construct a pedigree showing hairy earlobes* in a family *HE

-DETERMINE the oldest couple in the family-DRAW their pedigree symbols—include names-CONTINUE with other members in the family-DETERMINE genotypes as you gather enough information

Documents

11.1 BASIC PATTERNS OF HUMAN INHERITANCE