Unit 8-A Flashcards
Gene definition
Segments of DNA on a chromosome that code for a trait.
Alleles?
EXAMPLE?
- The different forms of a gene.
- Ex. Green pea pod allele or yellow pea pod allele
The Principle of Dominance
- Some alleles are dominant + others are recessive.
The Principle of Segregation
- Each gamete will only receive 1 copy of a gene in meiosis.
The Principle of Independent Assortment
- Each gene is inherited separately from others if they’re on different chromosomes
Dominant
- An allele (gene) that masks another.
- Predicts inheritance with a capital letter.
Recessive
- An allele (gene) that’s not observed when the dominant gene’s present
- Predicts inheritance with lowercase letter
What’s each trait determined by?
- Each trait is determined by 2 GENES (1 from EACH PARENT).
Genotype
- The gene combo for a trait
- Ex. RR, Rr, rr
Homozygous genotype (PURE)
- Gene combo involving 2 dominant/ 2 recessive genes. (Gene pair is the same)
- Ex. RR, rr
Heterozygous genotype (HYBRID)
- Gene combo of 1 dominant + 1 recessive allele. (Gene pair is different)
- Ex. Rr
Phenotype
- The physical appearance that results from the gene pair.
- Ex. Plant = green/yellow
Punnett Square
- Tool used to calculate genetic outcomes
Monohybrid Cross
- A genetic cross that compares only 1 trait
- Ex. Flower color
Dihybrid Cross
- A genetic cross that compares 2 different traits
- Ex. Flower color + plant height
Test cross
- A genetic cross between an unknown genotype and a homozygous recessive
Gregor Mendel
- An Austrian monk that worked on inheritance using garden peas.
- Father of Genetics
Mendel said that ____ ____ were inherited as particles. Particles are…
- Physical traits
- Particles are Chromosomes + DNA.
2 forms of alleles
- Dominant and Recessive
2 things that determine an organism’s characteristics?
GENES/DNA + ENVIRONMENT determine an organism’s characteristics.
How did Mendel get pure plants?
- He allowed them to self-pollinate for several generations
P1
- Parental generation in a breeding experiment.
F1 generation
- 1st generation offspring in a breeding experiment
F2 generation
- 2nd generation offspring in a breeding experiment
Phenotype is based on ___?
Phenotype is based on GENOTYPE & ENVIRONMENT
Incomplete dominance
- Neither allele is dominant or recessive.
- The heterozygous phenotype is a blending of traits.
- Ex. Red + white = pink flowers
Codominance
- Both alleles are expressed at the same time.
- The heterozygous phenotype will show both traits at the same time.
- Black + white = black + white feathers
Multiple Allele traits
- Traits determined by 2+ alleles.
Blood type is determined by…
- Blood type is determined by 3 alleles: I^a, I^b, and i.
- Multiple Allele trait
Polygenic traits
- Traits determined by 1+ gene.
Human skin color
- 4+ genes control this trait.
- Polygenic trait
Sex linked traits
- Traits (genes) that are carried on the X or Y sex chromosomes.
- Ex. Hemophilia + color blindness
Dominant disease
- Caused by a dominant allele
- Ex. Huntington’s
Recessive disease
- Caused by a recessive allele
- Ex. Cystic Fibrosis
How do you find the gametes for a dihybrid cross?
- FOIL
Most sex linked traits carried on what chromosome?
X chromosomes
Germ cell mutation
- Occurs in sex cells and can be passed on to offspring.
Somatic cell mutation
- Occurs in body cells and won’t be passed to offspring
Antigen
- A cell surface marker protein
- Proteins on the blood
Antibody
- A plasma protein that will attack similar antigens
Function of the heart
- Squeezes blood throughout the body in a closed loop.
Blood A
- A antigens
- Anti- B antibodies
- Can receive from A+O
- Can give to A and AB
Blood B
- B antigens
- Anti-A antibodies
- Can receive from B+O
- Can give to AB+B
Blood AB
- A+B Antigens
- No antibodies
- Can receive from all
- Can only give to AB
Blood O
- No antigens
- A+B antibodies
- Can receive from O
- Can give to all
Monohybrid Heterozygote cross ratios
- Phenotype ratio: 3:1
2. Genotype ratio: 1:2:1
Dihybrid Heterozygote cross ratio
- Phenotype ratio: 9:3:3:1
What are mutations caused by?
- Mutations are caused by mutagens like UV light or chemicals
Frameshift mutation
- A frame shift mutation occurs if 1+ nucleotides in DNA are added or deleted.
- This causes the codon sequence to be shifted
Female vs. Male Genotypes
- Female: XX
- Male: XY
