chapter 14 Mendel and the gene idea Flashcards
What scientific approach did Mendel use to identify laws of inheritance?
Mendel cross bred peas and tracked characteristics in two distinct forms
What are true-breeding varieties?
Varieties that produce offspring of the same variety when self-pollinated
What is hybridisation in Mendel’s experiments?
Mating two contrasting true-breeding varieties
What does the ‘P’ in P generation stand for?
Parental generation
What does the ‘F1’ generation refer to?
Hybrid offspring of the P generation
What is the F2 generation?
Offspring resulting from self or cross-pollinating F1 hybrids
What is the law of segregation?
The two alleles separate during gamete formation
What was the ratio of purple to white flowers in Mendel’s F2 generation?
3 to 1
What did Mendel call the purple flower color?
Dominant trait
What did Mendel call the white flower color?
Recessive trait
What is a ‘heritable factor’ according to Mendel?
What we now call a gene
What are alleles?
Alternative versions of a gene
What does the law of dominance state?
The dominant allele determines the organism’s appearance
What is a Punnett square used for?
To show possible combinations resulting from sperm and egg
Define homozygous.
Having 2 identical alleles
Define heterozygous.
Having 2 different alleles
What is a test cross used for?
To determine if a plant is homozygous dominant or heterozygous
What is a monohybrid?
Heterozygous for only one character/gene
What does the law of independent assortment state?
Each pair of alleles segregates independently to others
What is the phenotypic ratio resulting from crossing F1 dihybrids?
9:3:3:1
What is epistasis?
One gene alters the phenotypic expression of another gene
What is pleiotropy?
One gene influences multiple, seemingly unrelated phenotypic traits
What is multifactorial inheritance?
Genetic and environmental factors collectively influence phenotype
What is a recessively inherited disorder?
Exhibited only in individuals homozygous for the allele
What is albinism?
A recessive condition characterized by lack of pigmentation
What are dominantly inherited disorders?
Disorders caused by rare dominant alleles that arise by mutation
What is achondroplasia?
A form of dwarfism caused by a rare dominant allele
What is the challenge in studying human genetics?
Generation time is too long and breeding experiments are unacceptable
True or False: Carriers of recessive disorders display the disorder.
False
Fill in the blank: The four phenotypes of the ABO blood group are determined by three alleles for the enzyme (I) that attaches ______ carbohydrates to red blood cells.
A or B
What scientific approach did Mendel use to identify laws of inheritance?
Mendel used carefully designed experiments with garden peas.
What types of characteristics did Mendel track in his experiments?
Characteristics that occurred in two distinct forms.
What is hybridization in Mendel’s experiments?
The process of mating two contrasting, true-breeding varieties.
What happens when contrasting true-breeding white and purple flower plants are crossed?
All F1 hybrids were purple.
What ratio of purple to white flowers did Mendel observe in the F2 generation?
3 to 1.
What did Mendel conclude about the purple flower factor in F1 hybrids?
It was the only factor affecting flower color.
What are the terms for the traits Mendel identified in his flower experiments?
Purple flower color is a Dominant trait, white flower color is a Recessive trait.
What concept explains that alternative versions of a gene account for variations in inherited characters?
Alleles.
How many alleles does an organism inherit for each characteristic?
Two alleles, one from each parent.
What is the law of dominance?
The dominant allele determines the organism’s appearance.
What tool can show possible combinations resulting from sperm and egg?
Punnett square.
What is a test cross used for?
To determine whether an organism is homozygous dominant or heterozygous.
What does the law of independent assortment apply to?
Genes on different chromosomes or those far apart on the same chromosome.
What is non-mendelian inheritance?
Inheritance patterns that do not follow simple Mendelian genetics.
What is complete dominance?
Phenotype of heterozygote and dominant homozygote are identical.
What is incomplete dominance?
F1 hybrid phenotype is between the phenotypes of the two parents.
What is codominance?
Two dominant alleles affect the phenotype in distinguishable ways.
What can cause heterochromia iridium?
Excess or lack of melanin due to genetic mosaicism, chimerism, disease, or injury.
What factors influence phenotype?
Both genetic and environmental factors.
What is a multifactorial disorder?
A disease with both genetic and environmental components.
Why are humans not good subjects for genetic research?
Generation time is too long, parents produce few offspring, breeding experiments are unacceptable.
What characterizes recessively inherited disorders?
Exhibited only in individuals homozygous for the allele.
What is a carrier in genetics?
A heterozygous individual having the recessive allele but not displaying the disorder.
What is achondroplasia?
A form of dwarfism caused by a rare dominant allele.
