40 Questions
What is a karyotype?
A composite display of all of an organism’s chromosomes, illustrating sister chromatids, centromeres, and banding patterns
What is the function of a centromere in a chromosome?
To join sister chromatids
How many pairs of sex chromosomes do humans have?
2
What are the chromosomes of the 23rd pair in males?
X and Y
What is the term used to describe the situation in which the presence of a recessive allele is masked by the dominant normal allele?
Heterozygosity
Which term refers to how an allele behaves in combination with a recessive allele in a heterozygote?
Dominance
What term describes the situation where some dominant alleles are quite rare in a population?
Genetic drift
Which gene controls the number of human fingers and toes?
Polydactyly gene
What is the condition called when individuals have extra fingers and toes on each hand and foot?
Polydactyly
What type of dwarfism is caused by a very rare dominant allele in the human population?
Achondroplasia
What does Mendel's law of independent assortment state?
Alleles of different genes are distributed to egg and sperm cells independently of each other during meiosis.
What is the term for genes located on the same chromosome that may or may not be inherited together?
Linked genes
What is the term used to describe the situation when genes for different traits assort independently of each other during the formation of sperm and egg?
Independent assortment
What is the term for the ability of one gene to mask the effects of another gene?
Epistasis
What term describes the situation when a gene has more than two alleles in a population?
Multiple alleles
What is the term for the situation when one gene has multiple effects on the phenotype?
Pleiotropy
What is the term for alternative versions of genes due to small DNA sequence differences between autosomes?
Alleles
Which chromosomes carry genes unrelated to sex determination, such as those for color vision and blood clotting proteins?
X chromosomes
What is the term for the complete set of alleles that influences phenotype?
Genotype
What is the term for the collective genes and alleles in the human population?
Human gene pool
What did Gregor Mendel's experiments with pea plants lead to the discovery of?
Fundamental principles of inheritance and genes
What is the term for the discrete 'factors' of heredity proposed by Mendel, now known as genes, found on chromosomes?
Genes
What is the term for chromosomes that are inherited as a pair through meiosis and fertilization?
Sex chromosomes
What leads to genetic diversity in offspring?
Gametes receiving only one allele from each parent
What are homologous chromosomes with two copies of each gene inherited from each parent called?
Autosomes
What do different alleles of a gene have differences in?
Nucleotide sequence
What influences phenotype, including physical traits and susceptibility to diseases?
Genotype
What are small DNA sequence differences between autosomes that lead to alternative versions of genes called?
Alleles
In Mendel's experiments with pea plants, what did the cross of green and yellow pea plants result in?
Offspring producing all yellow peas
What did Mendel deduce about each pea plant's factors (alleles) for pea color?
Each pea plant has two factors for pea color, and each parent contributes only one factor to the offspring
What determines the freckles in humans, according to the text?
The MC1R gene
What is the inheritance pattern of cystic fibrosis?
Recessive
How does the yellow allele behave in pea plants, according to Mendel's experiments?
Dominantly
What is the genetic basis of most recessive alleles, according to the text?
They do not confer advantage or disadvantage
What is the outcome of inheriting two copies of the mutated CFTR gene?
Results in cystic fibrosis
How are harmful recessive alleles kept in check, according to the text?
By the occasional premature death of homozygous recessive individuals
What is the genetic basis of freckles, according to the text?
Dominant allele (F) for freckles and recessive allele (f) for no freckles
What is the genetic basis of cystic fibrosis, according to the text?
Recessive allele
What is the genetic basis of most recessive alleles, according to the text?
They do not confer advantage or disadvantage
What is the outcome of inheriting two copies of the mutated CFTR gene?
Results in cystic fibrosis
Study Notes
Inheritance and Genetic Variation
- Sex chromosomes differ in genes and function, but are inherited as a pair through meiosis and fertilization.
- The X chromosome carries genes unrelated to sex determination, such as those for color vision and blood clotting proteins.
- Autosomes are homologous chromosomes with two copies of each gene inherited from each parent.
- Small DNA sequence differences between autosomes lead to alternative versions of genes called alleles.
- Alleles may code for proteins with different structures and functions, affecting phenotype.
- Different alleles are a result of millions of years of mutations passed on through generations.
- The collective genes and alleles in the human population are known as the human gene pool.
- Genotype, the complete set of alleles, influences phenotype, including physical traits and susceptibility to diseases.
- Different alleles of a gene have differences in nucleotide sequence and are designated with uppercase and lowercase letters.
- Gametes receive only one allele from each parent, leading to genetic diversity in offspring.
- Gregor Mendel's experiments with pea plants led to the discovery of fundamental principles of inheritance and genes.
- Mendel proposed discrete "factors" of heredity, now known as genes, found on chromosomes.
Mendel's Experiments and the Principles of Inheritance
- Mendel's pea plant experiments provided insight into genetics in complex organisms
- Mendel performed a one-trait cross, following the inheritance of pea color
- Offspring from the cross of green and yellow pea plants all produced yellow peas
- When two yellow pea-producing offspring were crossed, 75% produced yellow peas and 25% produced green peas
- Mendel deduced that each pea plant has two factors (alleles) for pea color, and each parent contributes only one factor to the offspring
- A gamete (sperm or egg) is haploid and the allele a parent contributes is determined randomly
- The yellow allele behaves in a dominant manner, while the green allele is recessive
- The MC1R gene determines freckles, with a dominant allele (F) for freckles and a recessive allele (f) for no freckles
- Most recessive alleles do not confer advantage or disadvantage
- Cystic fibrosis is caused by a recessive allele, and only homozygous recessive individuals are afflicted
- The normal CFTR gene is dominant, and inheriting two copies of the mutated CFTR gene results in cystic fibrosis
- Harmful recessive alleles are kept in check by the occasional premature death of homozygous recessive individuals
Test your knowledge of inheritance and genetic variation with this quiz. Learn about sex chromosomes, alleles, genetic diversity, Mendel's experiments, and the principles of inheritance. Brush up on the fundamentals of genetics and understand how traits are passed down through generations.
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