Chap 17 Flashcards
Probability
A study of outcomes
Gregor Mendel
(1822-1884)
- demonstrated that heritable properties are divided in discrete units (genes) independently inherited
- used peas to “cross”
Law of segregation
Each gene separates (after crossing over) during gamete formation ~meiosis~ so each gamete only has one copy
- each parent contributes 1 allele for each gene to their offspring
- males and females contribute equally to the traits in their offspring
Selective breeding
A process in which people choose their breeding specific plants and animals for particular physical features or behaviours
Ex) wolf —-dog
True breeding
(Mendel)
- he allowed plants to self pollinate to ensure that they were “true-breeding” (parental/P)
• exhibits the same characteristics gen after gen
~offspring: first filial (f1)/ second filial (f2)
Mendel
Pollination and self pollination
Monohybrid cross
One trait involved in this type of cross
-hybrid: offspring of a cross between 2 parent organisms traits
Dominant
Mendel called these expressed characteristics dominant
-F1 generation
Recessive
Characteristic that was not expressed
Complete dominance
One form showed this over the other.
-An organism with one recessive and one dominant has same observable characteristics to an organism with two dominant forms
Law of segregation
Mendel first law
- genes = factors
- gametes receive one copy of gene
- each organism have copies of each gene
- egg+sperm dude randomly
- one copy from each parent
Genotype
Combination for alleles for any given trait (individual)
Phenotype
Physical form of observable trait expressed
Homozygous
An individual with 2 identical alleles for a trait
RR or rr
Heterozygous
An individual with 2 different alleles for a trait
Rr
Punnett square
A devised visual technique to analyse genotypes to determine the phenotypes
Test cross
Is a cross between the organism of unknown genotype and a homozygous recessive organism
Ex) Walter nice
Incomplete dominance
Describes a condition in which neither of two alleles for the same gene conceal presence of the other
-red&white flower= pink
Co-dominance
Is a situation in which both alleles are fully expressed
Ex) roan horde (half and half)
Dihybrid cross
Two genes involved in this type of cross
•opposite form of the same 2 traits
Law of independent assortment
Mendels second law.
-two alleles for one gene segregate/assort independently of of the alleles for other genes during gamete formation
Chromosome theory of inheritance
Walter Sutton published a paper proposing that genes are carried on chromosomes in 1902
Linked genes
Genes are found on the same chromosome called linked genes
-assort on a regular basis through crossing over
Crossing over
A random event that occurs with equal probability at nearly any point on a sister chromatid.
-more likely to occur between further appart genes than closer
Chromosome mapping
Process called mapping
-the concept that crossing over is used to determine the relative positions of genes in a chromosome
Map unit
Is defined distance between points on a chromosome where a crossover is likely to occur in 1% of all meiosis events
•map distance: distance between genes in a SINGLE Chromosome
Recombinant types
Flies that have different combinations of alleles that the chromosome of the P generation are an example.
-recombinants= # of recombinant types/total# of offspring x100%
Parental types
Flies that have chromosomes that are identical to those of the P generation
Recombination frequency
Percentage of flies that are recombinant types correspond to recombination frequency
•the percentage of times that a crossover occurred as P gametes were formed
Sex linked traits
Traits that are controlled by genes on either X or Y chromosome
Barr Body
The inactive chromosome is condensed into a structure tightly. (Every female cell or 1 X chromosome = inactive)
~random: which X chromosome
Multiple Alleles
A gene with more than two alleles
Ex) a clover (organism has 2+ alleles)
Order of dominance
Sequence that can be written as
C > Cch>Ch>C
(> means dominant)
Continuous traits
Traits for which the phenotype vary gradually from one extreme to another
- human height, ear length, corn
Polygenic traits
Traits that are controlled by many genes.
-polygenic= a group of genes that contribute to same traits
Gene mapping
The relative position of a he genes on the chromosome can be mapped using crossover frequency.
-drawing a map for given distanced between genes
Pedigree
Human Genetics can follow the inheritance of numerous generations within a family to study patterns of inheritance
-Genetics use a diagram called a pedigree to show the patterns of relationships and traits in a family over gens
Genetic Screening
the sequencing of human DNA in order to discover genetic differences, anomalies, or mutations that may prove pathological.
Genetic counsellor
Genetic counselors work as members of a healthcare team, providing risk assessment, education and support to individuals and families at risk for, or diagnosed with, a variety of inherited conditions
