Flashcards in Genetics Unit Test PPT. Deck (111):
study of genetics
- Study of how traits are passed from parent to offspring
- Father of Genetics
- Experimented with pea plant traits to follow inheritance
What structures does the perfect flower have?
male and female structures
- male structure
- produces pollen containing sperm
- female structure
- Produces ovules containing eggs
1. Grew pure plants (P generation) that had 2 of the same alleles.
2. Cross pollinated plants with contrasting traits to create F1 generation
3. Cross two F1 tall plants to get the F2
Law of Segregation
- During meiosis I homologous chromosomes separate.
- Offspring receives one gene for a trait from each parent.
- Used to predict the chances of offspring genotypes.
- Outcome is based on large number of offspring.
- P generation
- F1 generation (Hybrid 4:0)
- F2 generation (3:1 ratio)
Parental (P) generation
pure for a trait
Offspring of F1
Law of Independent Assortment
Inheritance of one trait has no effect on the inheritance of another trait when genes are on separate chromosomes
What are traits determined by?
the genes on the chromosomes
a segment of DNA that determines a trait
What do chromosomes come in?
What do genes come in?
matching genes – one from female parent and one from male parent
Example of Homologous Pairs:
Humans have 46 chromosomes or 23 pairs.
One set from dad – 23 in sperm
One set from mom – 23 in egg
different genes (possibilities) for the same trait –
ex: blue eyes or brown eyes
prevents the other allele from being expresses
is NOT expressed even though it is present in the DNA
symbol for dominant allele
upper case letter
symbol for recessive gene
lower case letter
How can a recessive trait be expressed?
Must have 2 recessive alleles for a recessive trait to be expressed
Always use the ____ letter for the same alleles.
Straight thumb is ______ to hitchhiker thumb
homozygous or purebred
Both genes of a pair are the same
TT – homozygous dominant
tt – homozygous recessive
heterozygous or hybrid
One dominant and one recessive gene
Tt – heterozygous
Combination of genes an organism has (actual gene makeup)
What is an example of a genotype?
Ex: TT, Tt, tt
Physical appearance resulting from gene make-up
What is an example of a phenotype?
Ex: hitchhiker’s thumb or straight thumb
What does probability mean?
The chance of an event occurring
In order to get close to the predicted, what do you have to many of?
NEED MANY TRIALS
What is the punnett square based on?
many offspring (trials)
What is the punnett square used for?
Used to predict the possible gene makeup of offspring
picture of an individual’s chromosomes
amniotic fluid surrounding the embryo is removed for analysis
variety of skeletal abnormalities
gradual deterioration of brain tissue, shows up in middle age and is fatal
What are dominant gene mutations?
- huntington's disease
- an amino acid common in milk cannot be broken down and as it builds up it causes mental retardation
- newborns are tested for this
mucous builds up in the lungs
- deterioration of the nervous system
- early death
What do mutated genes produce?
produce enzymes that are less effective than normal at breaking down fatty cell products known as gangliosides
What happens as result of what the mutated genes produced?
gangliosides build up in the lysosomes and overload cells. Their buildup ultimately causes damage to nerve cells
What are recessive gene mutations?
- sickle cell anemia
- Cystic fibrosis
- Tay-Sachs Disease
Sickle cell anemia
- red blood cells are sickle shaped instead of round and cannot carry enough oxygen to the body tissues
- heterozygous condition protects people from malaria
Gene or Point Mutation
- most common and least drastic
- only one gene is altered
What does the inside of punnett squares represent?
possible offspring (2N)
What does the outside of the punnett square represent?
Male gametes - N (One gene in sperm) or
Female gametes – N (One gene in egg)
What is the order to write a genotypic ratio?
homozygous dominant : heterozygous : homozygous recessive
What is the order to write a phenotypic ratio?
dominant : recessive
People have ___ chromosomes or ___ pairs.
determine body traits
22 pairs are _________.
What are the 22 homologous pairs called?
1 pair is a ____ chromosome
determines sex (male or female)
- sex chromosomes are homologous (look alike)
- label XX
- sex chromosomes are different
- label XY
What is the probability of a couple having a boy? Or a girl?
When one allele is NOT completely dominant over another they produce a blended phenotype
What is an example of incomplete dominance?
In carnations the color red (R) is incompletely dominant over white (W). The hybrid color is pink.
When both alleles are expressed individually
What is an example of complete dominance?
- In certain chickens black feathers are codominant with white feathers.
- Heterozygous chickens have black and white speckled feathers.
Red allele: R
White allele: W
Blood Type Alleles
Alleles for a protein on the Red Blood Cell
i^o or i
Possible Blood genotypes
- Type A
- Type B
- Type AB
- Type O
Sex determining Region of the Y
Genes for these traits are located only on the X chromosome (NOT on the Y chromosome)
Why are x-linked alleles expressed in males whether dominant or recessive?
males have only one X chromosome
What are examples of recessive sex-linked disorders?
inability to distinguish between certain colors
What is the most common type of color blindness?
red-green color blindness, where red and green are seen as the same color
blood won’t clot
- In females one X chromosome is inactivated in each cell.
- Some cells have one X turned off and some cells have the other X turned off.
Calico Cat color expression
Diagram of a trait passed through generations
horizontal lines =
Vertical line and brackets =
connect parent to offspring
A shaded circle or square =
person has the trait
A circle or square NOT shaded =
an individual who does NOT have the trait
Partial shade =
carrier/ heterozygous for the trait
3 or more alleles of the same gene that code for a single trait
In humans, blood types are determined by how many alleles?
3 alleles - A, B, and O
How many alleles from blood types do humans actually inherit?
inherit 2 alleles
Dominant Blood Type Alleles
A and B (codominance)
Recessive Blood Type Alleles
What are possible blood types?
A = AA or AO
B = BB or BO
AB = AB
O = OO
sudden genetic change (change in base pair sequence of DNA)
How can mutations be?
organism less able to survive: genetic disorders, cancer, death
allows organism to better survive: provides genetic variation
neither harmful nor helpful to organism
What are the two ways a mutation can occur?
chromosomal mutation or gene/point mutation
- less common than a gene mutation
- more drastic – affects entire chromosome, so affects many genes rather than just one
- caused by failure of the homologous chromosomes to separate normally during meiosis
- chromosome pairs no longer look the same – too few or too many genes, different shape
What are examples of chromosomal mutations?
- Down syndrome
- Turner's syndrome
- Klinefelter’s syndrome
(Trisomy 21) 47 chromosomes, extra chromosome at pair #21
- only 45 chromosomes, missing a sex chromosome (X)
- Girls affected – short, slow growth, heart problems
- 47 chromosomes, extra X chromosomes (XXY)
- Boys affected – low testosterone levels, underdeveloped muscles, sparse facial hair
What can happen if there is an extra set of chromosomes in animals?
fatal in animals