Chapter 11: Genetics Flashcards
What is the “particulate” hypothesis?
idea that parents pass on discrete heritable units (genes)
What is the “blending” hypothesis?
Genetic material from two parents blend together
Trait
specific characteristic that varies from one individual to another
Gene
sequence of DNA that coees for a protein and determines trait
Allele
one of a number of different forms of a gene
Hybrid
offspring of crosses between parents with different traits
True-breeding
organisms that produce offspring identical to themselves in order to self-pollinate
Mendel true-breeded
pea plants
Describe Mendel’s 1st of Dominance.
Two genes mixed = 1 Dominant gene shown in F1 generation
Segregation
separation of alleles during gamete formtion
- As the F1 plant flowers, the alleles are segregated so each gamete carries one single copy of that gene.
- Each f1 plant produces 2 TYPES of gametes.
Principle/Law of Independent Assortment
states that genes for different traits can segregate INDEPENDENTLY during the formation of gametes
- genes of one trait do not affect genes with other traits.
- this allows us to CROSS genes for different traits.
Cross Type: Two heterozygous
3 Dominant, 1 Recessive
Two heterozygous dihybrid cross gives a ratio of:
9:3:3:1
Incomplete dominance vs. codominance
For ex: Red x White flower
Incomplete dominance: Pink
Codominance: Red + White SPOTS
Which blood group has multiple alleles? (As an example)
ABO blood
Epistasis
one gene affects the expression of another
Polygenic inheritance
a single phenotypic character is affected by 2 or more genes
Pleiotropy
multiple phenotypic effects, possessed by most genes.
- responsible for multiple symptoms such as hereditary diseases
norm of reaction
the phenotypic range of a genotype influenced by the environment
- Ex: hydrangea flowers of same genotypic range from blue-violet to pink, depending on soil acidity
Polygenic trait
trait controlled by two or more genes
Diploid vs. Haploid
Diploid - contains both sets of homologous chromosomes
Haploid - contains only a single set of chromosomes and 1 single set of genes
Examples of diploid and haploid cells:”
Diploid: somatic (normal human body) cell
Haploid: sex cells or gametes
What does the ‘n’ represent?
of unique chromosomes
Homologous chromosomes
chromosomes that have a corresponding chromosome from the opposite-sex parent
- similar in shape, position, and information, but NOT IDENTICAL
Meiosis
separation of homologous chromosomes in a diploid cell
Synapsis
process of homologous chromsomes coming together during crossing-over
Tetrad
structure containing 4 chromatids that forms during meiosis.
Chiasmata
location where DNA is exchanged during crossing-over
Crossing-over
process in which homologous chromosomes exchange portions of their chromatids during meiosis
Spermatogenesis
formation of male gametes (sperm)
- 4 genetically different gametes
Oogenesis
formation of female gametes (egg)
- 4 genetically different gametes, but only 1 is functional
What was one thing that Mendel did wrong?
Genes don’t segregate independently, it’s chromosomes that undergo segregation and independent assortment.
Thomas Hunt Morgan’s discovery
first to associate a specific gene with a specific chromosome
Genome
full set of genetic material carried by an organism
Karyotype
set of photographs which shows complete diploid set of chromosomes
Autosome
autosomal chromosome; not a sex chromosome
sex chromosome
one of two chromosomes that determine an individual’s sex
- females = XX
- males = XY
Egg cells contain _____ chromosome. Sperm cells contain _____ chromosome.
Egg: 1 X chromosome
Sperm: 1 X or 1 Y chromosome
What determines the gender of an offspring?
the sperm cells
- about half of zygotes = 46 XX, and half will be 46XY.
Sex-Linked disorders are defective alleles on the __ chromosome.
X chromosome
- since the gene of these disorders is recessive, men are more likely to acquire this genetic disorder.
X-Chromosome Inactivation
Females can inactivate parts of an X chromosome and use the same genetic information from the corresponding chromosome
- spotted cats
