Trait
Observable characteristic
Alleles
Alternative choices for a gene (they code for the same gene, but one comes from mom and one comes from dad)
Dominant alleles [hide/are hidden by] a recessive allele
hide
Recessive alleles [hide/are hidden by] a dominant allele
are hidden by
Homozygous organisms have two of [the same/different] alleles for a trait
the same (ex. TT or tt)
Heterozygous organisms have two of [the same/different] alleles for a trait
different (ex. Tt)
Phenotype
character that is expressed; âway it looksâ
Genotype
genetic makeup; âwhat genes it hasâ
Generations labelled in punnett squares
P1 (parental) = true breeding parents in genetic cross
F1 (filial) = first filial generation, offspring of the P1
F2 (filial) = second filial generation, offspring of the F1
Mendelian Inheritance
Refers to certain patterns of how traits are passed from parents to offspring. Generally established by Gregor Mendel
Monohybrid crosses
cross to study only ONE character (ex. Aa x Aa)
Law of Segregation
Two alleles separate during gamete formation (separation of homologous partners during Anaphase I)
Dihybrid Cross
Cross to study TWO characters (ex. AaBb x AaBb)
Law of Independent Assortment
Each pair of alleles segregates (separate) independently in meiosis. Maternal and paternal chromosomes mix up in different combinations during gamete formation (Anaphase I)
Result of heterozygous cross (ex. AaBb x AaBb)
9:3:3:1 ratio
For trihybrid crosses or if parents are not heterozygousâŚ
Use multiplication and addition rules to determine ratios and probability of phenotypes
Possible different gamete combinations
2^n, where n= number of chromosome pairs
Testcross
Used to determine if an individual with dominant phenotype is heterozygous or homozygous.
Unknown genotype is crossed with homozygous recessive (A_ x aa)
Non-Mendelian Inheritance 1: Nature vs. Nurture
Environment influences phenotypic expression
(ex. Siamese cats/Himalayan rabbits - darker fur on areas that are cooler. Hydrangea flower color - depends on soil pH)
Non-Mendelian Inheritance 2: Spectrum of Dominance
Incomplete and co-dominance
Incomplete dominance
Heterozygote, blended intermediate phenotype (ex. red x white flowers; heterozygotes = pink)
Co-dominance
Both alleles are expressed at the same time (ex. Roan horse has BOTH white and red hair; AB blood typ)
Sex-linked Genes
X-linked -carried on X chromosome (ex. color blindness; hemophilia; Duchenne muscular Dystrophy)
Multiple Allele Trait
More than 2 choices (A, B, O blood alleles produce A, B, O, or AB blood types)
Polygenic Trait
Trait is determined by more than one gene (ex. skin color, intelligence, eye color)
Pleiotropy
One gene has multiple phenotypic effects (ex. dwarfism, cystic fibrosis)
Glycoproteins
On the surface of blood cells, determine blood type
True/false: It is important for doctors to know a personâs blood when performing a transfusion or transplant.
True
I^A and I^B are [recessive/codominant]
codominant
ii (type O) is [recessive/codominant] to A or B
recessive
Universal Donor
Type O
Universal Recipient
Type AB
Genetic Screening & Counseling
-Based on Mendelian genetics and probability rules
-Tests for identifying carriers
-Fetal testing
-Newborn screening
Carrier
Heterozygous individual that doesnât show trait, but can pass it on to offspring
Pedigree
Diagram that shows how traits are passed over generations
In a pedigreeâŚ
Female =
Male =
Individual with trait =
Carrier =
Female = circle
Male = square
Individual with trait = filled in
Carrier = half-shaded
Karyotype
Organizes picture of an individualâs chromosomes
Karyotypes can showâŚ
Sex: XX = female, XY = male
Some Genetic Disorders: missing/extra chromosomes (Down Syndrome, Turner Syndrome, Klinefelter Syndrome), large translocations/deletions (Fragile X)
Karyotypes cannot showâŚ
Gene mutations (ex. PKU, sickle cell)
Amniocentesis
A test that takes a sample of the amniotic fluid by sticking a needle into the abdomen and does biochemcial tests on it. This canât be done until 14-16 weeks and the whole process can take weeks. There is a risk of miscarriage if you go through this testing.
Chorionic Villus Sampling (CVS)
A testing during pregnancy that can be done once you are 8-10 weeks pregnant. Suction tube is is inserted through the cervix and biochemical tests/karyotyping can be done on fetal cells immediately. There are faster results than amniocentesis, but there is a greater chance of miscarriage than in amniocentesis