Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
Chapter 11 – Introduction to Genetics
Big Idea: Genetic information passes from parent to offspring during meiosis when gametes, each containing
one representative from each chromosome pair, unite.
11.1 – The Work of Gregor Mendel

An individual’s characteristics are determined by factors that are passes from one parental generation to
the next.

During gamete formation, the alleles for each gene segregate from each other so that each gamete carries
only one allele for each gene.
11.1 Vocabulary:

Genetics

Fertilization

Trait

Hybrid

Gene

Allele

Principle of Dominance

Segregation

Gamete
11.2 – Applying Mendel’s Principles

Punnett squares use mathematical probability to help predict the genotype and phenotype combinations
in genetic crosses.

The principle of independent assortment states that genes for different traits can segregate independently
during the formation of gametes.

Mendel’s principles of heredity, observed through patterns of inheritance, form the basis of modern
genetics.
11.2 Vocabulary:

Probability

Homozygous
Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
 Heterozygous

Phenotype

Genotype

Punnett Square

Independent Assortment
11.3 – Other Patterns of Inheritance

Some alleles are neither dominant nor recessive. Many genes exist in several different forms and are
therefore said to have multiple alleles. Many traits are produced by the interaction of several genes.

Environment conditions can affect gene expression and influence genetically determined traits.
11.3 Vocabulary:

Incomplete Dominance

Codominance

Multiple Allele

Polygenic Trait
11.4 – Meiosis

The diploid cells of most adult organisms contain two complete sets of inherited chromosomes and two
complete sets of genes.

In prophase I, replicated chromosomes pair with corresponding homologous chromosomes. At
metaphase I, paired chromosomes line up across the center of the cell. In anaphase I, chromosome pairs
move toward opposite ends of the cell. In telophase I, a nuclear membrane forms around each cluster of
chromosomes. Cytokinesis then forms two new cells. As the cells enter prophase II, their chromosomes
become visible. The final four phases of meiosis II result in four haploid daughter cells.
In mitosis, when the two sets of genetic material separate, each daughter cell receives one complete set
of chromosomes. In meiosis, homologous chromosomes line up and then move to separate daughter
cells. Mitosis does not normally change the chromosome number of the original cell. Meiosis reduces
the chromosome number by half. Mitosis results in the production of two genetically identical diploid
cells, whereas meiosis produces four genetically different haploid cells.


Alleles of different genes tend to be inherited together from one generation from the next when those
genes are located on the same chromosome.
11.4 Vocabulary:

Homologous
Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
 Diploid

Haploid

Meiosis

Tetrad

Crossing-over

Zygote
Chapter 12 – DNA
Big Idea: DNA is a double-stranded protein molecule made up of nucleotide base pairs. DNA stores, copies,
and transmits the genetic information in a cell.
12.1 – Identifying the Substance of Genes

By observing bacterial transformation, Avery and other scientists discovered that the nucleic acid DNA
stores and transmits genetic information from one generation of bacteria to the next.

Hershey and Chas’s experiment with bacteriophages confirmied Avery’s results, convincing many
scientists that DNA was the genetic material found in genes – not just in viruses and bacteria, but in all
living cells.

The DNA that makes up genes must be capable of storing, copying, and transmitting the genetic
information in a cell.
12.1 Vocabulary:

Transformation

Bacteriophage
12.2 – The Structure of DNA

DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds.

The clues to Franklin’s X-ray pattern enabled Watson and Crick to build a model that explained the
specific structure and properties of DNA.

The double-helix model explains Chargaff’s rule of base pairing and how the two strands of DNA are
held together.
12.2 Vocabulary:

Base Pairing
Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
12.3 – DNA Replication

DNA polymerase is an enzyme that joins individual nucleotides to produce a new strand of DNA.

Replication in most prokaryotic cells starts from a single point and proceeds in two directions until the
entire chromosome is copied.

In eukaryotic cells, replication may begin at dozens or even hundreds of places in the DNA molecule,
proceeding in both directions until each chromosome is completely copied.
12.3 Vocabulary:

Replication

DNA Polymerase

Telomere
Chapter 13 – RNA and Protein Synthesis
Big Idea: Messenger RNA, transfer RNA, and ribosomal RNA work together in prokaryotic and eukaryotic
cells to translate DNA’s genetic code into functional proteins. These proteins, in turn, direct the expression of
genes.
13.1 – RNA

The main differences between RNA and DNA are that (1) the sugar in RNA is ribose instead of
deoxyribose; (2) RNA is generally single-stranded, not double-stranded; and (3) RNA contains uracil in
place of thymine.

In transcription, segments of DNA serve as templates to produce complementary RNA molecules.
13.1 Vocabulary:

RNA

Messenger RNA

Ribosomal RNA

Transfer RNA

Transcription

RNA Polymerase

Promoter

Intron

Exon
Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
13.2 – Ribosomes and Protein Synthesis

The genetic code is read three “letters” at a time, so that each “word” is three bases long and
corresponds to a single amino acid.

Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains.

The central dogma of molecular biology is that information is transferred from DNA to RNA to protein.
13.2 Vocabulary:

Polypeptide

Genetic Code

Codon

Translation

Anticodon

Gene Expression
13.3 – Mutations

Mutations are heritable changes in genetic information.

The effects of mutations on genes vary widely. Some have little or no effect; some produce beneficial
variations. Some negatively disrupt gene function.

Mutations often produce proteins with new or altered functions that can be useful to organisms in
different or changing environments.
13.3 Vocabulary

Mutation

Point Mutation

Frameshift Mutation

Mutagen

Polyploidy
13.4 – Gene Regulation and Expression

DNA-binding proteins in prokaryotes regulate genes by controlling transcription.
Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
 By binding DNA sequences in the regulatory regions of eukaryotic genes, transcription factors control
the expression of those genes.

Master control genes are like switches that trigger particular patterns of development and differentiation
in cells and tissues.
13.4 Vocabulary

Operon

Operator

RNA Interference

Differentiation

Homeotic Gene

Homeobox Gene

Hox Gene
Chapter 14 – Human Heredity
Big Idea: Humans have 23 pairs of chromosomes, including one pair of sex chromosomes, that follow the same
patterns of Mendelian inheritance as do other organisms. Scientists study human heredity using karyotypes,
pedigrees, and Punnett squares, but they also use the tools of molecular biology and bioinformatics to study
DNA and gene expression. The Human Genome Project has revolutionized the study of human heredity.
14.1 – Human Chromosomes

A karyotype shows the complete diploid set of chromosomes grouped together in pairs, arranged in
order of decreasing size.

Human genes follow the same Mendelian patterns of inheritance as the genes of other organisms. Many
human traits follow a pattern of simple dominance. The alleles for other human genes display
codominant inheritance. Because the X and Y chromosomes determine sex, the genes located on them
show a pattern of inheritance called sex-linkage.

The information gained from pedigree analysis makes it possible to determine the nature of genes and
alleles associated with inherited human traits.
14.1 Vocabulary:

Genome

Karyotype

Sex Chromosome
Biology – Study Guide for 2nd Trimester Exam (Chapters 11 – 14)
 Autosome

Sex-linked Gene

Pedigree
14.2 – Human Genetic Disorders

Changes in a gene’s DNA sequence can change proteins by altering their amino acid sequences, which
may directly affect one’s phenotype.

If nondisjunction occurs during meiosis, gametes with an abnormal number of chromosomes may result,
leading to a disorder of chromosome numbers.
14.2 Vocabulary:

Nondisjunction
14.3 – Studying the Human Genome

By using tools that cut, separate, and then replicate DNA base by base, scientists can now read the base
sequences in DNA from any cell.

The Human Genome Project was a 13-year, international effort with the main goals of sequencing all 3
billion base pairs of human DNA and identifying all human genes.

The Human Genome Project pinpointed genes and associated particular sequences in those genes with
numerous diseases and disorders. It also identified about three million locations where single-base DNA
differences occur in humans.
14.3 Vocabulary:

Restriction Enzyme

Gel Electrophoresis

Bioinformatics

Genomics