Biology: Animals and Organisms
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Questions and Answers

What is the genotype of individuals who can roll their tongue?

RR or Rr

What is the rule in genetics to represent the dominant gene for tongue rolling?

  • Combination of letters
  • Numbers
  • Uppercase letter like R (correct)
  • Lowercase letter like r

    • A recessive gene is always expressed in the presence of a dominant gene.

    False

    ALLELES are alternative forms of a ___________.

    <p>gene</p> Signup and view all the answers

    What is the difference indicated by squares and circles in pedigree charts?

    <p>Males are represented by squares and females by circles.</p> Signup and view all the answers

    Which trait, free earlobe or attached earlobe, is dominant?

    <p>It is not specified in the given information.</p> Signup and view all the answers

    In which family are the parents heterozygous for the earlobe trait?

    <p>Family A</p> Signup and view all the answers

    Define heredity.

    <p>Heredity may be defined as the transmission of genetically based characteristics from parents to offspring.</p> Signup and view all the answers

    Which of the following are examples of characters and their traits? (Select all that apply)

    <p>Colour of the eyes - Brown or blue</p> Signup and view all the answers

    Genetics and heredity are the same thing.

    <p>False</p> Signup and view all the answers

    Like begets like and yet there are ______________.

    <p>variations</p> Signup and view all the answers

    What term did geneticist Wilhelm Johanssen coin in 1909 to describe the hereditary characteristics passed from parents to offspring?

    <p>gene</p> Signup and view all the answers

    Chromosome No. 1 has the largest number of genes with ____ (2968), and chromosome Y has the fewest with ____ (231).

    <p>2968</p> Signup and view all the answers

    What determines the hereditary characteristics of an organism?

    <p>Genes</p> Signup and view all the answers

    A recessive allele can only express itself in the presence of the same recessive allele.

    <p>True</p> Signup and view all the answers

    How many chromosomes are present in humans?

    <p>46</p> Signup and view all the answers

    What are homologous chromosomes?

    <p>Pairs of corresponding chromosomes of the same shape and size</p> Signup and view all the answers

    Sex chromosomes determine the general body features of an organism.

    <p>False</p> Signup and view all the answers

    Autosomes determine __________ body features like complexion and height.

    <p>general</p> Signup and view all the answers

    Match the following organisms with their chromosome numbers:

    <p>Humans = 46 Gorilla = 48 Dog = 38 Mouse = 40</p> Signup and view all the answers

    What is the term used to describe the ratio obtained from crossing for two different traits of a single character?

    <p>monohybrid ratio</p> Signup and view all the answers

    What are the phenotypic and genotypic ratios when crossing garden pea plants with terminal and axillary flowers?

    <p>Phenotypic ratio 3:1, Genotypic ratio 1:2:1</p> Signup and view all the answers

    What is the term for the appearance of an allele exclusively on the X chromosome or the Y chromosome?

    <p>Sex-linked inheritance</p> Signup and view all the answers

    Which genetic disorders are mentioned as more common in males than in females due to being located on the X chromosome? Select all that apply.

    <p>Haemophilia</p> Signup and view all the answers

    Colour blindness is an inherited disease that causes affected individuals to not differentiate between certain colors, mostly __________ and green.

    <p>red</p> Signup and view all the answers

    Criss-cross inheritance refers to the inheritance of X-linked genes from mother to daughter and father to son.

    <p>False</p> Signup and view all the answers

    Match the following individuals with their corresponding genetic conditions:

    <p>Carrier mother = XX° Colour-blind father = X°Y Haemophiliac male = X°X Normal daughter = XX</p> Signup and view all the answers

    What is the basic unit of heredity?

    <p>gene</p> Signup and view all the answers

    Define allele.

    <p>An allele is a variant form of a gene.</p> Signup and view all the answers

    Define genotype.

    <p>Genotype refers to the genetic makeup of an organism.</p> Signup and view all the answers

    Define phenotype.

    <p>Phenotype refers to the observable characteristics of an organism.</p> Signup and view all the answers

    How many paired chromosomes are there in a human male?

    <p>23</p> Signup and view all the answers

    Explain the concept of a heterozygous recessive.

    <p>A heterozygous recessive individual carries one dominant allele and one recessive allele for a particular trait.</p> Signup and view all the answers

    List four human characters along with their traits that can be easily studied using family charts.

    <p>Examples may include eye color, hair color, height, and blood type.</p> Signup and view all the answers

    How many kinds of ratios are mentioned in the two kinds of hybridizations?

    <p>Two kinds of ratios are mentioned: Phenotypic ratio and Genotypic ratio.</p> Signup and view all the answers

    What is the phenotypic ratio for monohybrid ratios in the F1 generation?

    <p>3:1</p> Signup and view all the answers

    What is the genotypic ratio for monohybrid ratios in the F1 generation?

    <p>1:2:1</p> Signup and view all the answers

    What is the phenotypic ratio for dihybrid ratios in the F1 generation?

    <p>3:1</p> Signup and view all the answers

    What is the genotypic ratio for dihybrid ratios in the F1 generation?

    <p>1:2:1</p> Signup and view all the answers

    Study Notes

    Heredity and Variation

    • Heredity is the transmission of genetically based characteristics from parents to offspring.
    • Variation refers to the differences among individuals of the same species.
    • Like begets like, meaning that cats produce cats, mango seeds germinate into mango trees, and humans give birth to humans.

    Characteristics and Traits

    • A character is a feature of an organism, while a trait is a variant of a character.
    • Examples of characters and traits include:
      • Eye color (brown or blue)
      • Hair shape (curly or straight)
      • Eyebrows (heavy, bushy, or thin)
      • Hair on the middle joint of fingers (growth or no growth)
      • Color vision (normal or red-green color blindness)
      • Tongue rolling (U-shape or no rolling)
      • Hand use (right-handedness or left-handedness)
      • Skin color (albinism or normal pigment)
      • Ear lobe (free or attached)
      • Lips (thick or thin)
      • Rh blood group (Rh positive or Rh negative)

    Chromosomes

    • Chromosomes are the carriers of heredity.
    • Humans have 46 chromosomes arranged in 23 pairs.
    • Chromosomes occur in even numbers and are always found in pairs.
    • Homologous chromosomes are pairs of chromosomes with the same shape and size, one inherited from each parent.
    • Autosomes are chromosomes that determine general body features, while sex chromosomes determine the sex of an organism.

    Karyotype

    • A karyotype is a chart that shows the arrangement of chromosomes in a cell nucleus.
    • Human karyotype shows 23 pairs of chromosomes.
    • Chromosomes are visible only during cell division.

    Autosomes and Sex Chromosomes

    • Autosomes are chromosomes that determine general body features, such as complexion, height, and seed color.

    • Humans have 22 pairs of autosomes.

    • Sex chromosomes (also called allosomes) determine the sex of an organism.

    • Humans have only one pair of sex chromosomes (XY in males and XX in females).### Sex Determination

    • The sex of a child is determined by the type of sperm that fertilizes the egg, not by the mother's ability to produce only daughters.

    • Eggs contain only X chromosomes, while half of the sperms released are X-bearing and the other half are Y-bearing.

    • When an X-bearing sperm fertilizes an egg, the resulting combination is XX, i.e., a female constitution.

    • When a Y-bearing sperm fertilizes an egg, the resulting combination is XY, i.e., a male constitution.

    Genes and Genome

    • Genes are specific parts of a chromosome that determine hereditary characteristics.
    • The genome is the full complement of DNA, including all genes and intergenic regions, of an organism.
    • Humans have nearly 19,000 genes, with chromosome 1 having the largest number (2968) and chromosome Y having the fewest (231).

    Genes and Their Alleles

    • Genes have two alternative forms, called alleles, which produce different effects.
    • Dominant alleles express themselves regardless of the presence of another allele.
    • Recessive alleles are suppressed in the presence of a dominant allele.
    • Example: The gene for tongue rolling has two alleles, one for rolling and one for non-rolling.

    Genotype and Phenotype

    • Genotype refers to the genetic constitution of an organism, i.e., the kinds of genes it possesses.
    • Phenotype refers to the expressed characteristics of an organism, which are genetically controlled.
    • Example: For the phenotype of tongue rolling, there are two genotypes: RR (homozygous dominant) and Rr (heterozygous dominant).

    Inheritance

    • The gene for tongue rolling is located on a particular pair of chromosomes.
    • Every individual has a pair of this gene, which can be represented as RR, Rr, or rr.
    • The genotype of an individual determines the phenotype, which is the observable characteristic.### Punnett Square and Inheritance
    • A Punnett square is a simple diagram used to illustrate the possible combinations of gametes (sex cells) from two parents.
    • The square is divided into sub-squares, with the gametes from one parent along one side and the gametes from the other parent along the other side.
    • The resulting genotypes and phenotypes can be written in the sub-squares.

    Tongue Rolling Inheritance

    • The ability to roll the tongue is an inherited trait.
    • A pedigree (family) chart can be used to show the inheritance of this trait.
    • In the pedigree chart, males are represented by squares and females are represented by circles.
    • Both parents are tongue rollers (hollow symbols), but their children can have different genotypes (RR, Rr, or rr).

    Dominant and Recessive Traits

    • A dominant trait is one that is expressed when an individual has one or two copies of the dominant gene.
    • A recessive trait is one that is expressed only when an individual has two copies of the recessive gene.
    • Examples of dominant and recessive traits include:
      • Eye color: brown (dominant) and blue (recessive)
      • Tongue rolling: rolling (dominant) and non-rolling (recessive)
      • Hand clasping: right-handed (dominant) and left-handed (recessive)
      • Ear lobe attachment: free (dominant) and attached (recessive)

    Heterozygous and Homozygous

    • An individual who is heterozygous for a trait has two different forms of the gene (e.g. Rr).
    • An individual who is homozygous for a trait has two identical forms of the gene (e.g. RR or rr).

    Inheritance of Ear Lobe Attachment

    • The inheritance of ear lobe attachment can be explained using a pedigree chart.
    • In family A, both parents have free ear lobes (dominant), and their children can have free or attached ear lobes.
    • In family B, both parents have attached ear lobes (recessive), and their children all have attached ear lobes.

    Polydactyly

    • Polydactyly is a rare genetic trait that results in extra fingers or toes.
    • The trait is dominant, meaning that an individual only needs to inherit one copy of the gene to express the trait.
    • An extreme case of polydactyly is shown in the example of a 15-month-old boy with 7 fingers on each hand and 10 toes on each foot.

    Sex-Linked Inheritance

    • Sex-linked inheritance refers to the inheritance of traits that are linked to the X chromosome.
    • The X chromosome carries genes that are responsible for certain traits, such as color vision.
    • Inheritance of these traits follows a specific pattern, as shown in the example of a color-blind father and a normal mother.

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