BJU Life Science Chapter 7
What is an inherited disorder?
an abnormal trait passed on through genes
In genetics what is meant by the expression "making a cross"?
a controlled mating of organisms to test how inherited traits are passed down
What is a Punnett square?
a graphical way of showing different traits and how they could combine
What do the letter combinations in the boxes of Punnett square represent?
possible gamete combinations (genotypes) of the offspring
What is a gamete?
a reproductive cell that contains half of the normal amount of chromosomes - it is haploid
How many chromosomes does a normal human cell have?
46, or 23 pairs
Explain the difference between an organism's phenotype and its genotype.
Phenotype refers to an organism's phsyical characteristics - what it looks like. Genotype refers to the specific factors an organism possesses.
What do the letters that are placed along the top and side of the Punnett square represent?
Possible gametes from the parents. Letters representing the possible gametes from one parent are placed along the top, and those from the other parent are place along the side.
What is a sex-linked trait? Give an example
a trait that has a gene on the X chromosome but no corresponding gene on the Y chromosome. Red-green color blindness.
What are Mendel's factors called today?
genes
Define multiple gene inheritance. Give an example
more than two genes are responsible for producing a single trait. Hair color maybe controlled by as many as 12 different pairs of genes.
Define incomplete dominance. Give an example.
two traits combine or blend together to produce a different trait. Red and white snapdragons produce pink flowers
name two methods of learning about unborn children.
ultrasound, fetoscope, amniocentesis
What is a carrier?
people who have a gene for a trait but do not express the trait themselves
Define hybrid
1. offspring of 2 genetically unrelated individuals 2. an organism having factors that are different (one dominant/one recessive)
Define purebred
1. an organism in which the genetic traits have remained the same for many generations 2. an organism having identical factors (genes) for a trait
give examples of inherited traits
1. humans: eye color, hair color, hair texture, chin shape 2. pea plants: height, color of pod, color of pea, texture of pea
List 3 variations to single dominant/recessive inheritance patterns
1. incomplete dominance 2. codominance 3. multiple gene inheritance
Why are males more likely to have sex-linked disorders than females?
Males have only one X chromosome. If they receive a recessive gene for a disorder, they do not have another X chromosome that could contain the dominant form of the gene.
Describe Mendel's work with the genetics of peas.
Mendel cross bred purebred pea plants with opposite traits. He grew the hybrid offspring of that cross (the F₁ generation) and let those plants self-pollinate. He then grew the seeds from the hybrid plants, producing the F₂ generation. He observed and documented the traits expressed and wrote a set of theories to explain the data. One theory said that traits were controlled by factors.
How is sex inherited in humans?
The 23rd chromosome pair determines sex. These are known as the sex chromosomes. Females will have 2 X's and males will have an X and a Y.
What is a zygote?
a cell formed from the union of two gametes
How could you produce a hybrid by using purebred organisms?
cross, or mate, purebred organisms that have opposite traits
Define codominance. Give an example.
dominant and recessive traits are both expressed. In shorthorn cattle, red hair and white hair are burebred. The hybrid animal has both red and white in its coat. This coloration is called roan. Another example is feather color in Andalusian chicken - white, black, or dark blue which is a mix of the black and white
Whose gamete determines the sex of the child in humans?
the father's sperm. An X chromosome from a sperm will produce a female and a Y chromosome from a sperm will produce a male.
What is genetics?
the study of inherited traits