Week 14-Genetics Flashcards
What is a chromosome?
the DNA molecule is packaged into thread-like structures called chromosomes
How many chromosomes do human cells have and where did they come from?
46- 23 pairs
23 from oocyte and 23 from sperm
What occurs and what is the significance of “crossing over” during meiosis?
It happens when paired homologs, or chromosomes of the same type, are lined up
They will connect and exchange some genetic information
This information should be at the same location on the chromosomes
This allows for genetic variation in the gamete
What are autosomes?
first 22 Pairs of chromosomes
determine all other body features
What are the sex chromosomes?
23rd chromosome
determines sex of baby
What is X inactivation? Why is it important?
While males get one X, females get 2 x’s
Females will have to completely turn off one X
important because it allows for women to not have twice the amount of genes that they are supposed to have
The first 22 pairs of chromosomes are each paired homologous chromosomes. What does this mean?
Each chromosome pair will code for same type of information
so information on male side of chromosome 1 is same as info on female side of chromosome 1
What is a gene?
unit on a chromosome that codes for a specific trait
Where are specific genes located?
chromosomes
What do genes code for?
specific traits/ proteins
What does it mean when someone has a “genetic” disease or disorder?
Someone has abnormal genes or chromosomes
somewhere something went wrong to make mutations
Genotype
genetics/genes in person
what you are made of
Phenotype
What you show physically
physical characteristics
Describe an allele. Do all genes (characteristics) have alleles?
alternate forms of a trait
(tongue rolling or not tongue rolling)
(dimples or no dimples)
Describe simple inheritance involving dominant and recessive alleles (dominant allele and recessive allele)
one allele is dominant and one is recessive
dominant allele will be the one that will be demonstrated on human
dominant will completely mask the recessive allele
What does it mean to be homozygous for a trait that has 2 alleles?
Both parents gave you dominant or both recessive
Same alleles
DD
or
dd
What does it mean to be heterozygous for a trait that has 2 alleles?
One parent gave dominant and one recessive
Different Alleles
Dd
Briefly describe co-dominance inheritance.
More then 1 allele that has dominance
Briefly describe polygenic (complex) inheritance.
Many genes contribute to a trait
environmental factors can affect as well
Give an example of Co-Dominance inheritance
Blood typing-
A and B are dominant
O is recessive
Only way to have O blood is to be completely recessive, if just one A and/or B appears then that is your blood type
Give an example of Polygenic inheritance
eye color
skin color
hair color
Be able to fill in and interpret a Punnet square (predict inheritance)—per class project
______D d
D | DD Dd
d | Dd dd
How is an Autosomal Recessive genetic disorder typically inherited?
When both parents carry one recessive allele unknowingly and child gets both recessive alleles
Father and mother both Rr, child gets rr genetics from them
What does it mean to be a carrier of a recessive genetic disorder?
Have the receive disorder allele
Must be either Rr or rr
where r= recessive and R=dominant
What is the significance of an Autosomal Dominant genetic disorder—what would the inheritance pattern be?
very Rare
Dominant allele will always show- so most people who show genetic disorder choose to not have kids
in Huntington- shows in age 45, so father may not even realize he has it until already has kids
all you need is the one dominant allele to get this disease
What is sex-linked (X-linked) inheritance?
inheritance pattern comes from sex chromosome, not the first 22
Describe inheritance of a recessive X linked disorder.
mom will more likely give recessive allele to boys
mothers get two x’s and turn one off, boys only get one x,
if mother accidentally gives recessive x allele to child then they might get it as well without being able to turn it off
Describe why the sperm determines sex of the offspring
Mother will always give X chromosome (XX)
father could either give x or y(XY), meaning boy(XY) or girl(XX)
Missesnse mutation
Base substitution
Codes for wrong amino acid
nonsense mutation
Base substitution
Codes for stop codon
silent mutations
Base substitution
Still get same amino acid
insertion mutation
Frameshift mutation
insert a base-results in all bases shifting completely forward 1
deletion mutation
Frameshift mutation
a base deletes- results all bases shifting completely back 1
duplication mutation
Frameshift mutation
a portion of the DNA is abnormally copied one or more times
triplet mutation
repeat expansion
will keep repeating same codon
(ccg,ccg,ccg,ccg)
Differentiate between a spontaneous mutation
Random mistakes that occur at a low rate
in replication of dna
Differentiate between a induced mutation
produced by agents called mutagens
Mutagens will increase the mutation rate above
the spontaneous mutation rate
What is a chromosomal abnormality?
something that affects the entire chromosome
so all 10,000 proteins on it
What occurs in a numerical chromosomal
abnormality?
Should have 23 pairs- 2 on each pair
If you have an extra chromosome on one pair
(extra chromosome on pair 2 = Down syndrome)
Why are there so few chromosomal disorders?
Most do not allow for development of embryo - so baby would die before it was born
