BIO EXAM FOUR STUDY GUIDE SMC

What is a gene?

A unit of DNA that encodes information needed to produce proteins, cells, and entire organisms.

What is the locus of a gene?

The location of a gene on a chromosome.

How many chromosomes do human cells contain?

46 chromosomes, or 23 pairs.

What are autosomes?

Non-sex chromosomes; humans have 22 pairs of autosomes.

What are homologous chromosomes?

A pair of chromosomes that contain similar genes.

What are alleles?

Alternative versions of genes found at the same gene locus.

What does it mean if an organism is homozygous at a locus?

Both homologous chromosomes carry the same allele at that locus.

What does it mean if an organism is heterozygous at a locus?

The two homologous chromosomes carry different alleles at that locus.

What method predicts offspring genotypes and phenotypes?

The Punnett square method.

Who discovered the principles of inheritance?

Gregor Mendel.

Why did Mendel choose pea plants for his experiments?

Pea plants have distinct traits and can self-fertilize.

What is a genetic cross?

The mating of pollen and eggs from the same or different parents.

What is the parental generation in Mendel's experiments?

The original plants used in a cross, known as the P generation.

What is the first filial generation?

The offspring of the parental generation, known as F1.

What ratio was observed in Mendel's F2 generation for flower color?

3/4 purple-flowered plants and 1/4 white-flowered plants, a ratio of 3:1.

What is true-breeding?

Plants that are homozygous for a particular characteristic and always produce the same phenotype.

What is Mendel's law of segregation?

The pairs of alleles on homologous chromosomes separate during meiosis.

What is the significance of dominant and recessive alleles?

The dominant allele may mask the recessive allele in the presence of both.

What trait did Mendel find to be dominant in pea plants?

The purple-flower trait is dominant over the white-flower trait.

What determines which allele is included in a gamete?

Chance during meiosis, as homologous chromosomes separate at random.

What are true-breeding organisms?

Organisms that have two copies of the same allele for a given gene and are homozygous.

What is the genotype?

The particular combination of two alleles carried by an individual.

What is the phenotype?

The physical expression of the genotype, such as purple or white flowers.

What does the allele 'P' represent?

The dominant purple-flowered allele.

What is the result of a cross between a purple-flowered plant (PP) and a white-flowered plant (pp)?

All purple-flowered F1 offspring with a Pp genotype.

What is a test cross?

A cross used to determine if an organism with a dominant phenotype is homozygous or heterozygous.

What happens if a dominant-phenotype organism is homozygous dominant (PP) in a test cross?

Only dominant-phenotype offspring will be produced.

What happens if a dominant-phenotype organism is heterozygous (Pp) in a test cross?

Approximately half the offspring will be of recessive phenotype.

How is sex determined in mammals?

By a set of sex chromosomes; females have XX and males have XY.

What determines the sex of the offspring in mammals?

The sex chromosome carried by the sperm.

What is incomplete dominance?

A pattern of inheritance where the heterozygous phenotype is intermediate between the two homozygous phenotypes.

What are the possible hair types from two wavy-haired parents?

Curly (C1C1), wavy (C1C2), or straight (C2C2).

What is codominance?

When heterozygotes express the phenotypes of both homozygotes.

What are the human blood types?

A, B, AB, and O.

What alleles produce blood type A?

AA or Ao genotypes.

What alleles produce blood type B?

BB or Bo genotypes.

What is the result of having the oo genotype?

Blood type O.

What is the effect of the environment on phenotype?

The environment can profoundly affect the expression of genes.

What is nondisjunction?

The incorrect separation of chromosomes in meiosis.

What is trisomy 21?

A genetic disorder where individuals have three copies of chromosome 21, known as Down syndrome.

What are some characteristics of Down syndrome?

Weak muscle tone, small mouth, distinct eyelids, low resistance to diseases, and varying degrees of mental retardation.

What are genes made of?

Nucleic acid (DNA).

What are genes?

Units of heredity made of nucleic acid (DNA).

What are nucleic acids made of?

Polymers of nucleotides linked by dehydration synthesis reactions.

What are the components of a nucleotide?

A sugar, a phosphate group, and a nitrogenous base.

What forms the backbone of nucleic acids?

The sugar and phosphate groups.

What is the directionality of the nucleic acid backbone?

3' versus 5'.

What do the nitrogenous bases in DNA represent?

The genetic information.

What are the two families of nitrogenous bases?

Pyrimidines and Purines.

What is Chargaff's rule?

Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C).

Who discovered the double helix structure of DNA?

Watson and Crick.

What did Rosalind Franklin contribute to the understanding of DNA?

Provided physical structure evidence that led to the double helix model.

How long is DNA in a typical human cell?

About 2 meters long.

What percentage of human DNA encodes mRNAs or other RNAs?

About 1.5%.

What are mini-satellite sequences?

Single nucleotide differences in sequence between individuals of the same species.

When did forensic DNA analysis become commercially available?

In 1987.

What is recombinant DNA?

The combination of DNA from two or more organisms into a single DNA molecule.

How is insulin produced using recombinant DNA technology?

The gene for insulin is inserted into E. Coli, which then produces insulin.

What is the role of Human Growth Hormone (HGH)?

Increases protein synthesis, burning of body fat, and growth.

What does Erythropoietin (EPO) do?

Stimulates red blood cell production.

What is the significance of the crystal spore produced by bacteria?

It is harmless to plants and humans but deadly to insects.

What are featherless chickens?

Chickens developed through recombinant technology believed to lower market preparation costs.

What is DNA replication?

The process of copying DNA prior to cell division.

What enzyme separates DNA strands during replication?

Helicase.

What is the role of DNA polymerase?

Synthesizes new DNA strands in the 5' to 3' direction.

What is the difference between leading and lagging strand synthesis?

Leading strand is synthesized continuously, while lagging strand is synthesized in pieces.

What is transcription?

The process of synthesizing RNA using DNA as a template.

What is messenger RNA (mRNA)?

RNA synthesized from a gene coding for a protein.

What are the main differences between DNA and RNA?

DNA is double-stranded, contains deoxyribose, and thymine; RNA is single-stranded, contains ribose, and uracil.

What is the process of synthesizing RNA from DNA called?

Transcription

What is the RNA synthesized from a gene coding for a protein called?

Messenger RNA (mRNA)

What sugar is found in DNA?

Deoxyribose

What sugar is found in RNA?

Ribose

Which base in DNA is replaced by uracil in RNA?

Thymine

What is the process of synthesizing proteins from RNA called?

Translation

What do transfer RNA (tRNA) and ribosomal RNA (rRNA) do?

Act as interpreters between mRNA and amino acids

How many nucleotides are there in RNA?

4

How many amino acids are there?

20

What is a codon?

A 3-nucleotide sequence that specifies an amino acid

How many codons code for amino acids?

61 of the 64 possible codons

What are stop codons?

The remaining 3 codons that signal the translation to stop

What is the order of steps in the transcription process?

Initiation, elongation, termination

What binds to the promoter region of DNA to start transcription?

RNA polymerase

What happens at the termination signal during transcription?

RNA polymerase detaches from the DNA and releases the RNA molecule

Where does protein synthesis occur?

On the ribosomes outside the nucleus

What is the role of tRNA in protein synthesis?

To transfer the correct amino acid to the ribosome

What is the start codon for translation?

AUG

What is a point mutation?

A mutation limited to one or two nucleotides in a single gene

What is insertion in the context of mutations?

The insertion of one or more nucleotide pairs into a gene

What is deletion in the context of mutations?

The deletion of one or more nucleotide pairs from a gene

What is evolution?

A change in the genetic makeup of a population over time

Who published 'On the Origin of Species'?

Charles Darwin

What did early explorers reveal about life?

A staggering diversity of life.

What role did naturalists play during explorations?

They catalogued the plant and animal life found.

What did the vast number of species observed allow naturalists to see?

Patterns that had not emerged before.

What did fossils reveal about life?

Life has changed over time.

What are fossils?

Preserved remains or traces of organisms that died long ago.

In what type of rock are most fossils found?

Sedimentary rock.

Who recognized that certain fossils were always found in the same layers of rock?

William Smith.

What did the organization of fossils and rock layers indicate?

Fossils of a given type are always in the same layers.