Heredity

Question What is heredity? tap to flip ↻ Answer The transmission of traits from parents to offspring. Question What are the units of heredity called? tap to flip ↻ Answer Genes. Question What is the difference between genotype and phenotype? tap to flip ↻ Answer Genotype is the genetic makeup (alleles present), while phenotype is the observable physical or biochemical characteristics. Question Define allele. tap to flip ↻ Answer Alternative forms of a gene that occupy the same locus on homologous chromosomes. Question What is a dominant allele? tap to flip ↻ Answer An allele that expresses its phenotype even when only one copy is present (heterozygous). Question What is a recessive allele? tap to flip ↻ Answer An allele that expresses its phenotype only when two copies are present (homozygous). Question State Mendel's Law of Segregation. tap to flip ↻ Answer During gamete formation, the two alleles for a trait separate so that each gamete carries only one allele. Question State Mendel's Law of Independent Assortment. tap to flip ↻ Answer Alleles of different genes assort independently of one another during gamete formation. Question What is a monohybrid cross? tap to flip ↻ Answer A cross between two individuals that differ in one trait (e.g., tall vs. short). Question What is a dihybrid cross? tap to flip ↻ Answer A cross between two individuals that differ in two traits (e.g., seed shape and color). Question What phenotypic ratio is observed in the F2 generation of a monohybrid cross? tap to flip ↻ Answer 3:1 (dominant:recessive). Question What is the genotypic ratio in the F2 generation of a monohybrid cross? tap to flip ↻ Answer 1:2:1 (homozygous dominant : heterozygous : homozygous recessive). Question What is the phenotypic ratio in the F2 generation of a dihybrid cross? tap to flip ↻ Answer 9:3:3:1. Question What is a test cross? tap to flip ↻ Answer A cross between an individual with an unknown genotype and a homozygous recessive individual to determine the unknown genotype. Question What is incomplete dominance? tap to flip ↻ Answer A condition where the phenotype of the heterozygote is intermediate between the two homozygotes. Question What is codominance? tap to flip ↻ Answer A condition where both alleles express themselves fully in the heterozygote. Question What are multiple alleles? tap to flip ↻ Answer More than two alleles for a gene exist in a population, though an individual can have only two. Question What is pleiotropy? tap to flip ↻ Answer A single gene affects multiple phenotypic traits. Question What is polygenic inheritance? tap to flip ↻ Answer A trait controlled by multiple genes, often showing continuous variation. Question What is a karyotype? tap to flip ↻ Answer A visual arrangement of chromosomes from a cell, showing their number and structure. Question What is the chromosomal basis of sex determination in humans? tap to flip ↻ Answer Males are XY and females are XX; the male gamete determines the sex of the offspring. Question What is a sex-linked gene? tap to flip ↻ Answer A gene located on a sex chromosome, often the X chromosome. Question What is a mutation? tap to flip ↻ Answer A sudden change in the DNA sequence that can alter gene function. Question What is a pedigree chart? tap to flip ↻ Answer A diagram showing the inheritance of a trait across generations in a family. Question What is the difference between homozygous and heterozygous? tap to flip ↻ Answer Homozygous has two identical alleles for a gene; heterozygous has two different alleles. Question What is a carrier in genetics? tap to flip ↻ Answer An individual who is heterozygous for a recessive trait and does not show the phenotype but can pass the allele to offspring. Question What is the F1 generation? tap to flip ↻ Answer The first filial generation, offspring of the parental (P) generation. Question What is the F2 generation? tap to flip ↻ Answer The second filial generation, offspring of the F1 generation. Question What is a Punnett square? tap to flip ↻ Answer A diagram used to predict the genotypes and phenotypes of offspring from a cross. Question What is the law of dominance? tap to flip ↻ Answer In a heterozygote, one allele (dominant) masks the expression of the other (recessive). Question What are the two types of chromosomes based on function? tap to flip ↻ Answer Autosomes (non-sex chromosomes) and sex chromosomes (X and Y). Question What is nondisjunction? tap to flip ↻ Answer Failure of chromosomes to separate properly during meiosis, leading to gametes with abnormal chromosome numbers. Question What is a genetic disorder? tap to flip ↻ Answer A disease caused by abnormalities in genes or chromosomes. Question What is the genotype of a person with blood group AB? tap to flip ↻ Answer $I^A I^B$ Question What is the genotype of a person with blood group O? tap to flip ↻ Answer $ii$ Question What is the phenotypic ratio of a test cross between a heterozygous tall plant and a homozygous short plant? tap to flip ↻ Answer 1:1 (tall:short). Question What is the probability of a child being male in humans? tap to flip ↻ Answer 50% (1/2). Question What is the chromosomal abnormality in Down syndrome? tap to flip ↻ Answer Trisomy of chromosome 21 (three copies). Question What is the chromosomal abnormality in Turner syndrome? tap to flip ↻ Answer Monosomy of X chromosome (45, X0). Question What is the chromosomal abnormality in Klinefelter syndrome? tap to flip ↻ Answer Extra X chromosome in males (47, XXY). Question What is the difference between autosomes and sex chromosomes? tap to flip ↻ Answer Autosomes are non-sex chromosomes (22 pairs in humans); sex chromosomes determine sex (1 pair). Question What is the significance of Mendel's work? tap to flip ↻ Answer He established the fundamental laws of inheritance through experiments on pea plants. Question Why did Mendel choose pea plants for his experiments? tap to flip ↻ Answer They are easy to grow, have clear contrasting traits, and can be self-pollinated or cross-pollinated. Question What is the difference between a trait and a character? tap to flip ↻ Answer A character is a feature (e.g., height), while a trait is a specific form of that character (e.g., tall or short). Question What is a hybrid? tap to flip ↻ Answer An offspring resulting from a cross between two genetically different individuals. Question What is the law of independent assortment based on? tap to flip ↻ Answer The random alignment of homologous chromosome pairs during metaphase I of meiosis. Question What is the probability of a homozygous recessive offspring from a cross between two heterozygous parents? tap to flip ↻ Answer 25% (1/4). Question What is the probability of a heterozygous offspring from a cross between a homozygous dominant and a homozygous recessiv… tap to flip ↻ Answer 100%. Question What is the genotype of a carrier for a recessive disorder? tap to flip ↻ Answer Heterozygous (one dominant normal allele, one recessive mutant allele). Question What is the difference between a monohybrid and a dihybrid cross? tap to flip ↻ Answer Monohybrid involves one trait; dihybrid involves two traits. Question What is the expected phenotypic ratio in the F2 of a dihybrid cross if genes are linked? tap to flip ↻ Answer Not 9:3:3:1; it deviates due to linkage. Question What is linkage? tap to flip ↻ Answer The tendency of genes on the same chromosome to be inherited together. Question What is recombination? tap to flip ↻ Answer The process by which genetic material is rearranged, producing new allele combinations. Question What is the role of crossing over in heredity? tap to flip ↻ Answer It increases genetic variation by exchanging segments between homologous chromosomes. Question What is a sex-linked disorder? tap to flip ↻ Answer A disorder caused by a gene on a sex chromosome, often X-linked. Question Why are X-linked recessive disorders more common in males? tap to flip ↻ Answer Males have only one X chromosome, so a single recessive allele on X expresses the disorder. Question What is the genotype of a colorblind male? tap to flip ↻ Answer $X^c Y$ Question What is the genotype of a carrier female for colorblindness? tap to flip ↻ Answer $X^C X^c$ Question What is the probability of a colorblind son from a carrier mother and normal father? tap to flip ↻ Answer 50% of sons will be colorblind.