Abcte Biology

Front 1

gametes

Back 1

a reproductive cell containing a haploid chromosome or half of the genetic material needed for the formation of a new organism through fusion with another gamete cell

Front 2

dominant traits

Back 2

any trait expressed over another

Front 3

genes

Back 3

the set of information that controls a trait

Front 4

alleles

Back 4

different forms of a gene

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homozygous

Back 5

presence of the same allele at the same locus; a genotype of identical alleles of a gene, either homozygous dominant (SS) or homozygous recessive (ss)

Front 6

heterozygous

Back 6

presence of different alleles at the same locus; a genotype of different alleles of a gene, being heterozygous (Ss)

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phenotype

Back 7

the observable, expressed genes of an organism

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genotype

Back 8

the entire genetic constitution of an organism that does not show as outward characteristics

Front 9

The alleles an individual carries are part of the individual’s

A phenotype
B genotype
C gametes
D DNA

Back 9

The correct choice is B. An individual’s genotype describes its entire genetic makeup, including all its alleles. Phenotype refers to those traits that are physically expressed and visible in the individual. As not all alleles are visibly expressed, choice A is not correct. Gametes are sex cells, so choice C is incorrect. Alleles are made up of DNA; they are not a part of it, so choice D is not correct.

Front 10

Which of the following indicates an individual that is heterozygous for two traits?

A AABB
B AaBB
C AaBb
D aabB

Back 10

The correct choice is C. This individual carries both dominant (A, B) and recessive (a, b) alleles for each trait. Choice A is incorrect because this individual carries pairs of identical dominant alleles for each trait. Choice B is not correct because this genotype indicates that the individual is homozygous (BB) for one trait. Choice D is incorrect because this individual, too, is homozygous recessive (aa) for one trait.

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Punnett Square

Back 11

allows you to sort and visualize the distribution of alleles in any cross. Capital letters indicate dominance. Lowercase letters indicate recessive alleles.

Front 12

What ratio did Mendel use to determine that allelles sorted independently of one another?

Back 12

9:3:3:1. The 9 represents the number of F 2 offspring expressing the two dominant traits in its phenotype. The 1 represents the proportion of offspring that express the recessive phenotype (having two alleles for the recessive form of the trait). The two 3s represent individuals that show combinations of recessive and dominant traits in their phenotype. (This ratio holds for crosses in which both parents are homozygous—one for dominant traits and the other for recessive traits.)

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law of independent assortment

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the transmission of traits, independent of each other, to offspring

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loci

Back 14

the specific position of a gene on the surface of a chromosome

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chromosomes

Back 15

a threadlike linear strand (eukaryotic cells) or circular strand (bacteria) of DNA that contains hereditary information

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pedigree

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a record of an organism's lineage (ancestors and descendants) used to determine certain gene patterns or disease inheritance; usually illustrated in a pedigree chart

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sex-linked

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a gene coded on a sex chromosome

Front 18

A pedigree chart is helpful for which medical reason

A tracing genealogy.
B predicting the sex of future offspring.
C tracing causes of death.
D tracking inherited genotypes and phenotypes.

Back 18

The correct choice is D. Pedigree charts allow you to track the carriers of a gene in their genotype and those offspring who express the gene in their phenotype. Genealogy does not track the presence or absence of genes, so choice A is not correct. Choice B is incorrect because a pedigree chart cannot help you predict the genotype of future offspring unless you know the genotype of future mates. Choice C is incorrect because just tracing the cause of death may not involve the inheritance of genes.

Front 19

autosomal

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any chromosome other than a sex chromosome

Front 20

A sex-linked condition is

A an abnormal condition in an offspring’s reproductive system
B a condition that is passed from mothers to sons
C a condition that is passed from fathers to sons
D an abnormal number of sex chromosomes in offspring

Back 20

The correct choice is B. A sex-linked condition, such as hemophilia, is passed from mothers to sons. Choice A is incorrect because a sex-linked condition does not refer to the offspring’s reproductive system, but to genetic inheritance. Choice C is not correct because a sex-linked condition comes from a mother’s genes, not a father's. Choice D is not correct because a sex-linked condition does not affect the number of sex chromosomes in offspring.

Front 21

An offspring will suffer from an autosomal recessive condition only if

A it has the dominant gene for that condition
B it is heterozygous for the gene that causes the condition
C it is homozygous for the gene that causes the condition
D it has inherited the recessive genes from its mother

Back 21

The correct choice is C. An offspring must have two copies of the recessive gene for it to be expressed—for the condition to appear. If the condition is caused by autosomal recessive genes, then a dominant gene would ensure that the recessive cause of the condition was not expressed, so choice A is not correct. If an offspring is heterozygous for the genes that cause the condition, the offspring has one dominant and one recessive gene for the condition. Thus, the dominant gene would ensure that the disease was not expressed, so choice B is incorrect. Choice D is incorrect because an offspring inherits only one allele from its mother.