Chapter 8 Flashcards
Genetics
The study of the transmission of traits (alleles) from one generation to the next (from parents to offspring)
Study of inheritance
Gene
A sequence of DNA nucleotides that codes for a specific protein (feature of an organism )
There is at least one gene for every feature (characteristic)
Allele
one of two or more versions of a gene that determines a particular trait for a characteristic
Recessive
describes a trait whose expression is masked by another trait when the alleles for both traits are present in an individual
Dominant
describes a trait that masks the expression of another trait when both versions of the gene are present in an individual
Genotype
the underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism
Phenotype
The observable traits or physical expression of genotype
The characteristic we see
Heterozygous
having two different alleles for a given gene on the homologous chromosomes
Homozygous
having two identical alleles for a given gene on the homologous chromosomes
Assign genotypes using D and d
Homozygous dominant?
Homozygous recessive?
Heterozygous?
DD
dd
Dd
Do all alleles for all genes exhibit a complete dominant/ recessive relationship?
No
Codominance
Both alleles are equally and fully expressed in the heterozygous
complete and simultaneous expression of both alleles for the same characteristic
Incomplete dominance
in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype
3 options
Punnet square
a visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid
Genotypes for males and females with x-linked traits?
Red-Green Colorblind:
X^b X^b
X^b Y
Carrier:
X^B X^b
Normal:
X^B X^B
X^B Y
How mitosis and meiosis fit into the human life cycle ?
Pass on genes and eggs, sperm that contain the instructions
Gregor Mendel
Discover the fundamental laws of inheritance
Which is better, dominant or recessive alleles?
Depends on the gene
A dominant gene is not necessarily better than recessive gene
Among lethal alleles, which is rarer dominant or recessive alleles?
Dominant lethal alleles are rarer
Múltiple alleles
More than two genes present on a chromosome
Environmental factors
Traits can be affected by both genetic and environmental factors
Environment can alter the effects of genes
Environmental factors examples?
Tanning and skin color
Nutrition and height
Exercise and physique
Experience and IQ tests
Sex-linked genes
Genes located on the sex chromosomes
X-linked: located on the X, but not Y
Y-linked: located on the Y, but not X
X-linked genes patterns pedigree
Males always inherit their X from their mother
Males more likely to express recessive X-linked traits than females
Only females can be carriers of X-linked recessive traits
Autosomal pedigree
Two unaffected parents produce an affected child
Recessive trait skips a generation, producing completely unaffected individuals
Two affected parents only have affected children
