118 Questions
What is the term for the transmission of traits from one generation to the next?
Heredity
What is the unit of heredity made up of segments of DNA?
Gene
What is the specific location of each gene on a certain chromosome?
Locus
Who is known as the father of Genetics?
Gregor Mendel
What is the term for the scientific study of heredity and variation?
Genetics
What are the reproductive cells called that pass genes to the next generation?
Gametes
What did Gregor Mendel use to identify the basic principles of heredity?
Garden peas
What is the term for the differences in appearance that offspring show from parents and siblings?
Variation
What is the term for an organism with two different alleles at a locus?
Heterozygote
What is the result of the segregation of alleles during gamete formation?
Gametes with one allele
What is the purpose of a Punnett square?
To predict the results of a genetic cross
What is the ratio of the genotype of the F2 generation in a cross between two heterozygotes?
1:2:1
What is the term for the physical appearance of an organism?
Phenotype
Why is it difficult to determine the genotype of an individual with the dominant phenotype?
Because it can be either homozygous or heterozygous
What is the purpose of a testcross?
To determine the genotype of an individual with the dominant phenotype
What is the genetic makeup of an individual with the recessive phenotype?
pp only
According to the Punnett square, what is the probability of the offspring having the YR genotype in an F2 generation?
1/4
What is the result of the hypothesis of independent assortment?
Genes are located on different chromosomes
What is the ratio of the phenotypic trait in an F2 generation when the P generation is YYRR and the F1 generation is heterozygous?
9:3:3:1
What is an example of incomplete dominance?
Palomino horses
What is the term for the process of separation of homologous chromosomes in meiosis?
Anaphase I
What is an example of codominance?
Human blood group types
What is the result of the law of segregation?
The alleles of a gene segregate into gametes independently
What is the term for the probability of different genotypes in the offspring based on the genotypes of the parents?
Punnett square
What is the main difference between normal and abnormal hemoglobin molecules in sickle cell anemia?
Mutated gene structure
What is the probability that the offspring will have thalassaemia if one parent is a carrier?
25%
What is the characteristic of cystic fibrosis that affects the pancreas?
Scarring and cyst formation
What is the frequency of cystic fibrosis in people of European descent?
1 in 2,500
What is the result of the cystic fibrosis allele in plasma membranes?
Defective or absent chloride transport channels
What is the name of the disorder caused by variants in CTR1, a high-affinity copper transporter?
A newly identified disorder of copper metabolism
What is the characteristic of sickle cell anemia that affects the shape of red blood cells?
Deformation into a sickle shape
What is the type of genetic disorder that cystic fibrosis is classified as?
Autosomal recessive
What is the principle of independent assortment?
Genes for different traits can segregate independently during gamete formation
What type of inheritance pattern is observed when a red carnation and a white carnation produce offspring that are all pink?
Incomplete dominance
What is the expected outcome of a TT x Tt crossing, if the allele for tall plants (T) is dominant and the allele for short plants is recessive (t)?
¾ tall; ¼ short
What is the expected phenotype of the offspring of a BW x WW crossing, if the hair colour in rabbits shows an incomplete dominance pattern of inheritance?
2 white: 2 beige
Which of the following statements describes best autosomal dominant disorders?
They are expressed in every generation
Which type of genetic disorder is caused by mutations in the mitochondrial DNA?
Mitochondrial
What is the mode of inheritance of Haemophilia?
X-linked recessive
What is the characteristic of autosomal recessive disorders?
They require two copies of the mutated allele to be expressed
What is the type of inheritance that involves the interaction of multiple genes to produce a single phenotype?
Polygenic inheritance
What is the term for the range of phenotypes that can be expressed by a genotype due to environmental influences?
Norm of reaction
How many pairs of chromosomes are found in human somatic cells?
23
What is the purpose of a pedigree?
To predict the probability of specific phenotypes
What is the term for the chromosomes that do not determine the sex of an individual?
Autosomes
What is the number of chromosomes found in a human karyotype?
46
What is the purpose of a dihybrid cross in Mendel's experiment?
To determine if two characters are inherited together or independently
What is the term for the study of the inheritance of traits and variation?
Genetics
What is the condition for the law of independent assortment to apply?
If two genes are located on different chromosomes
What is the characteristic of multifactorial characters?
Influenced by both genetic and environmental factors
What is the outcome of the law of independent assortment?
Each pair of alleles segregates independently of each other during gamete formation
What is the result of the crossing of two F1 dihybrids?
Producing offspring with multiple combinations of traits
What is the relationship between genes located on the same chromosome?
They are inherited together
What is the purpose of studying the inheritance of seed colour and shape?
To determine if the traits are inherited independently
What is the number of possible combinations of chromosomes in gametes in a dihybrid cross?
2^n, where n is the haploid number of chromosomes
What is the significance of the dihybrid cross in understanding heredity?
It helps to understand the law of independent assortment
What is the main difference between the alleles of the genes for seed color and shape in the P generation?
They are on non-homologous chromosomes
What is the result of the independent assortment of alleles during gamete formation?
The alleles segregate independently
What is the genotype of the F1 plants?
YyRr
What is the law of segregation describing?
The separation of alleles during gamete formation
What is the ratio of the phenotypic traits in the F2 generation?
9:3:3:1
What is the result of cross-fertilization in the F1 generation?
All offspring are heterozygous
What is the purpose of the diagrams in Figure 15-2?
To illustrate the law of independent assortment
What is the significance of the Y and y alleles?
They are dominant and recessive alleles
What is the consequence of a mutation in the haemoglobin gene?
Deformation of red blood cells into a sickle shape
What is the characteristic of the cystic fibrosis allele?
Results in defective or absent chloride transport channels
What is the frequency of cystic fibrosis in people of European descent?
1 in 2,500
What is the probability that the offspring will have thalassaemia if one parent is a carrier?
25%
What is the name of the disorder caused by variants in CTR1, a high-affinity copper transporter?
A newly identified disorder of copper metabolism
What is the characteristic of thalassaemia?
Due to a mutation in the haemoglobin gene
What is the result of the cystic fibrosis allele in the small intestine?
Abnormal absorption of nutrients
What is the inheritance pattern of cystic fibrosis?
Autosomal recessive
What is the function of CTR-1 protein?
To facilitate the transport of copper in the intestinal epithelial cells
What is a characteristic of autosomal recessive disorders?
The affected individuals usually do not survive until adulthood to produce offspring
What is the name of the disorder caused by dominant alleles that express symptoms late in life?
Huntington's disease
What is the characteristic of X-linked recessive disorders?
They are much more common in men than women due to the absence of the allele on the Y chromosome
What is the purpose of genetic counseling?
To provide information to prospective parents concerned about a family history for a specific disease
What is the result of the screening policy in Cyprus for β-thalassemia?
It has reduced the number of children born with the hereditary blood disease from 1 in 158 births to almost zero
What is the characteristic of X-linked dominant disorders?
They are extremely rare and usually fatal
What is the term for the transmission of traits from one generation to the next?
Inheritance
What is the role of the enzyme encoded by the i allele in the ABO blood group?
Adds neither A nor B carbohydrate
What is the phenomenon where the effects of one gene are modified by one or several other genes?
Epistasis
What is the result of the cc homozygote genotype in mice?
No coat colour
What is the relationship between the frequency of dominant and recessive alleles in a population?
The frequency of dominant and recessive alleles can vary in a population
What is the term for the property of most genes to have multiple phenotypic effects?
Pleiotropy
What determines the phenotypic expression of the gene responsible for coat colour in mice?
Two genes with multiple alleles each
What is the reason why one allele has no noticeable effect on the appearance of an organism?
Because it is a recessive allele
What is the effect of the genotype 'cc' on the coat color in an individual?
It prevents the deposition of pigment, resulting in a white color
What is the purpose of a Punnett square?
To predict the results of a genetic cross between individuals of known genetic makeup
What is the term for the inheritance of a single phenotype controlled by two or more genes?
Polygenic inheritance
What is the characteristic of albinism, a human genetic disorder?
It is a congenital autosomal recessive disorder characterized by the complete or partial absence of pigment
During meiosis, what happens to the 2 alleles for a gene?
They separate and end up in different gametes
What is the role of the gene that codes for tyrosinase in albinism?
It produces melanin
What is the relationship between genotype and phenotype in an organism?
An organism's traits do not always reveal its genetic composition
What is the term for the process of separating homologous chromosomes in meiosis?
Meiosis
What is the effect of the albinism allele on the expression of genes responsible for hair and eye color?
It inhibits the expression of these genes
What is the characteristic of quantitative characters in polygenic inheritance?
They vary in the population along a continuum
Why is it difficult to determine the genotype of an individual with the dominant phenotype?
Because the genotype cannot be determined from the phenotype
What is the main characteristic of polygenic inheritance?
Continuous variation
What is the term for the environmental influence on the phenotype of an organism?
Norm of reaction
What is the number of chromosomes in a human somatic cell?
23 pairs of chromosomes
What is the purpose of a pedigree analysis?
To predict the probability of specific phenotypes
What is the term for the chromosomes that determine the sex of an individual?
Sex chromosomes
What is the characteristic of multifactorial characters?
Influence of both genetic and environmental factors
What is the term for the display of the pairs of chromosomes in a cell?
Karyotype
What is the characteristic of polygenic characters?
Continuous variation
What is the purpose of studying the inheritance of traits and variation?
To understand the mechanisms of evolution
What is the term for the physical appearance of an organism?
Phenotype
What is the primary function of the CTR-1 protein?
To transport copper ions
What is the characteristic of autosomal recessive disorders?
They can be expressed in the phenotype even if one normal allele is present
Why are autosomal dominant disorders less common than autosomal recessive disorders?
Because affected individuals usually die before mating and passing the gene on
What is the difference between X-linked recessive and X-linked dominant disorders?
X-linked dominant disorders are more common than X-linked recessive disorders
What is the purpose of genetic counseling?
To provide information to prospective parents about the risk of passing a genetic disorder to their offspring
What is the characteristic of multifactorial disorders?
They have both genetic and environmental components
What is the result of the screening policy in Cyprus for β-thalassemia?
A decrease in the incidence of β-thalassemia
What is the characteristic of Huntington's disease?
It is a late-onset disease with no obvious phenotypic effects until the individual is about 35 to 40 years of age
What is the purpose of carrier detection?
To test for identifying carriers of various diseases
What is the characteristic of CTR-1 deficiency?
It is an autosomal recessive disorder
Test your understanding of human genetics by taking this quiz on karyotypes, pedigrees, and Mendelian inheritance. Learn about the concepts of karyotype and pedigree, Mendel's laws of segregation and independent assortment, and autosomal dominant vs recessive inheritance. Identify the role of genetic testing in human genetic disorders.
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