Bio 1101 chapter 10, 11, 12

How many homologous pairs are there?

23 pairs

How many total chromosomes are there?

46

ZYGOTE

A cell that is capable of developing into an adult organism. The zygote is formed when an egg is fertilized by a sperm.

ESTROGENS

A class of sex hormones, including estradiol, that are higher in women than in men and support female sexual development and function.

ANDROGENS

A class of sex hormones, including testosterone, that are present in men and cause male-associated traits like deep voice, growth of facial hair, and defined musculature.

PUNNETT SQUARE

A diagram used to determine probabilities of offspring having particular genotypes given the genotypes of the parents.

PROTO-ONCOGENE

A gene that codes for a protein that helps cells divide normally.

TUMOR SUPPRESSOR GENE

A gene that codes for proteins that monitor and check cell cycle progression. When these genes mutate, tumor suppressor proteins lose normal function.

ONCOGENE

A mutated and overactive form of a proto-oncogene. Oncogenes drive cells to divide continually.

If a mutation occurs during DNA replication in an adult skin cell, is a new allele formed?

A new allele could be formed if the error is not corrected during cell cycle checkpoints.

BENIGN TUMOR

A noncancerous tumor that will not spread throughout the body.

MALIGNANT TUMOR

A noncancerous tumor that will not spread throughout the body.

HOMOLOGOUS CHROMOSOMES

A pair of chromosomes that both contain the same genes. In a diploid cell, one chromosome in the pair is inherited from the mother, the other from the father.

x- linked trait

A phenotype determined by an allele on an X chromosome.

Gene

A section of DNA that may contain the instructions for assembling amino acids together into a polypeptide chain. There may be several alternate versions of the instructions.

Chromosomes

A single, long DNA molecule (wrapped around special proteins) that contains the individual instructions for many different proteins.

Can you think of a situation when genes would not be inherited in pairs (*hint: think of sex determination

A situation when genes would not be inherited in pairs is shown when looking at the sex chromosomes X and Y. For example, males inherit one X chromosome from their mother and one Y chromosome from their father, thus only having one copy of the chromosomes, and thus genes, of X and Y.

MEIOSIS

A specialized type of nuclear division that generates genetically unique haploid gametes.

Pedigree

A visual representation of the occurrence of phenotypes across generations.

DOMINANT ALLELE

An allele that can mask the presence of a recessive allele

RECESSIVE ALLELE

An allele that reveals itself in the phenotype only if a masking dominant allele is not present

Allele

An alternate version of a gene.

EMBRYO

An early stage of development reached when a zygote undergoes cell division to form a multicellular structure.

RECOMBINATION

An event in meiosis during which maternal and paternal chromosomes pair and physically exchange DNA segments.

CARRIER

An individual who is heterozygous for a particular gene of interest and, therefore, can pass on the recessive allele without showing any of its effects.

CARCINOGEN

Any chemical agent that causes cancer by damaging DNA. Carcinogens are a type of mutagen.

MUTAGEN

Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.

At which point during the cell cycle do BRCA1 and BRCA2 proteins function? Given their function, explain why they operate at this stage of the cycle and not at an earlier or later stage.

BRCA1 proteins are most likely active during the S Phase of the cell cycle because they are DNA repair proteins and it is during the S Phase that DNA replication happens

Why is it advantageous for an organism to have two copies of every gene?

Because genes are inherited in pairs, it provides, in essence, a backup system where if one gene is mutated and nonfunctional, the other normal gene may be able to compensate for the loss.

what are the three major ways in which an individual may acquire DNA mutations?

DNA mutations can be inherited, they can arise through mistakes in DNA replication, and they can be directly caused by environmental insults (mutagens and carcinogens like smoking and UV light).

What are some measures a person can take to reduce their risk of hereditary cancers? How do these measures reduce cancer risk?

For hereditary cancers, the DNA mutation is already present. There are still some things a person can do, however, to reduce their risk of developing cancer. They could elect to be genetically screened for specific mutations, the results of which may influence other activities in their lives (for example, a person may quit smoking if they find they have a mutation that predisposes them to lung cancer). If a deleterious mutation is confirmed (aka a mutation that has been associated with the development of cancer, like a mutation in the BRCA1 gene), the person could elect to have prophylactic surgery to remove the tissue that is likely

HAPLOID

Having only one copy of every chromosome

HETEROZYGOUS

Having two different alleles for a given gene.

HOMOZYGOUS

Having two identical alleles for a given gene.

Why do mutated proto-oncogenes increase cancer risk?

Mutated proto-oncogenes (or oncogenes) increase cancer risk because they are now continually "turned on" and stimulate the cell to divide uncontrollably.

Why do mutated tumor-suppressor genes increase cancer risk?

Mutated tumor-suppressor genes increase cancer risk because they can no longer pause the cell cycle when there are mistakes in the DNA or cause apoptosis, so the damaged cell is allowed to continue through the cell cycle to grow and divide.

Will a child inherit the following mutations from their parent? Why or why not? - A mutation in the father's testes caused by gamma radiation that causes the production of more testosterone and thus more sperm cells.

No, although this mutation affects the LEVEL of a germ-line cell (in this case, sperm) it is still a mutation in a somatic cell and is not passed on to offspring.

Will a child inherit the following mutations from their parent? Why or why not? - A mutation in the father's skin caused by sun damage.

No, this is a mutation of a somatic cell (nongamete).

In general, will any mutation that produces a dysfunctional protein increase cancer risk? Explain.

Not necessarily. For cancer cells to develop, the mutation would have to result in a dysfunctional protein that somehow caused the deregulation of the cell cycle leading to uncontrolled proliferation.

Which characteristics can differ between a gene and its mutated allele? Choose all that apply.

Nucleotides, Amino acids, Shape, Length

In many organisms, including humans, chromosomes occur in homologous pairs; where does each member of the pair originate

One chromosome comes from your mother, and the other comes from your father.

Protein

One or more chains of amino acids connected in a specific order and taking on a particular shape that is functional.

How does the final number of daughter cells produced compare to the starting number of cells? What about the starting number of chromosomes compared to the resulting daughter cell chromosome number?

One original cell with four chromosomes results in four daughter cells, each with two chromosomes. So, starting from one cell with four chromosomes, you end up with four cells with two chromosomes each.

autosomes

Paired chromosomes present in both males and females; all chromosomes except the X and Y chromosomes.

sex chromosomes

Paired chromosomes that differ between males and females. Females have XX, and males have XY.

GONADS]

Sex organs: ovaries in females, testes in males.

Mutations in DNA can be caused by

Smoking cigarettes, Heredity, UV sun tanning beds, Char

GAMETES

Specialized reproductive cells that carry one copy of each chromosome (that is, they are haploid). Sperm are male gametes; eggs are female gametes.

How many times does the cell divide during meiosis?

The cell divides twice. Once during meiosis I and once during meiosis II.

Can you determine by looking at the diagram how the chromosomes are arranged and ordered when a karyotype is prepared?

The chromosomes are numbered based on size. The largest (chromosome 1) to the smallest (chromosome 22) with the sex chromosomes (X and Y) at the end

Y-chromosome analysis

The comparison of sequences on the Y chromosomes of different individuals to examine paternity and paternal ancestry.

If a mutation that occurs during DNA replication is not corrected as a sperm cell is generated, is the new allele passed on to the next generation?

The new allele would be passed on to the next generation.

GENOTYPE

The particular genetic makeup of an individual.

At which point during the cell cycle is a proto-oncogene most likely to operate? Explain your reasoning.

The point at which a proto-oncogene is most likely active is at the initiation of the cell cycle or G1 because a proto-oncogene promotes cell division in response to appropriate signals.

INDEPENDENT ASSORTMENT]

The principle that alleles of different genes are distributed independently of one another during meiosis.

Explain why the symbol for proto-oncogenes is a green "go," whereas the symbol for tumor suppressors is a red "stop."

The symbol for proto-oncogenes is a green "go" because the normal function of these genes is to signal cells to progress through the cell cycle. In contrast, the symbol for tumor suppressors is a red "stop" because the normal function of these genes is to signal the cells to pause during the cell cycle to fix mistakes.

[PHENOTYPE

The visible of measurable features of an individual.

Phenotype

The visible or measurable features of an individual

Why does a person with an inherited mutation in a proto-oncogene more likely to develop cancer at a younger age?

They require fewer additional mutations to develop cancer.

What are some measures a person can take to reduce their risk of cancer? How do these measures reduce cancer risk?

To reduce their cancer risk, a person could wear sunblock to limit their exposure to UV radiation, thus preventing mutations caused by this mutagen. They could also avoid smoking cigarettes that contain many carcinogens that could mutate their DNA.

True or False: Tumor suppressor genes suppress tumors by pausing the cell cycle so a dividing cell can make repairs.

True

Given that most chromosomes occur in homologous pairs, do most genes also occur in pairs?

Yes, because chromosomes are long stretches of DNA containing gene sequences.

Can your personal lifestyle choices affect your likelihood of acquiring DNA mutations? Explain.

Yes, personal lifestyle choices can affect your likelihood of acquiring DNA mutations. For example, a person who repeatedly tans in a tanning booth with no sunblock is exposing him/herself to a high amount of UV light, which may cause mutations. Or the risk of acquiring DNA mutations is very high for someone who chooses to smoke cigarettes. These are personal choices that can affect the amount of DNA mutation that occurs throughout a person's life.

Will a child inherit the following mutations from their parent? Why or why not? • A mutation caused by a chemical that affects the mother's egg cells.

Yes; this is a mutation of a germ-line cell (gamete).

Where does each member of the gene pair come from?

You inherit one chromosome (and thus genes) from your mother and one chromosome (and thus genes) from your father.

MUTATION

a change in the nucleotide sequence of DNA

GERM-LINE MUTATION

a mutation occurring in gametes; passed on to offspring

SOMATIC MUTATION

a mutation that occurs in a body cell

One of the mutations that causes CF, discussed in the text, results from the deletion of ______ in the CFTR gene, which causes the _______ of an amino acid in the CFTR protein, thus making it nonfunctional

an entire codon / omission

True or False: A mutation in a proto-oncogene that causes the protein to be nonfunctional will lead to cancer.

false

True or False: A person who has a mutation in their BRCA2 gene will develop breast cancer at some point in their life.

false

True or False: In terms of size, from largest to smallest, the units of inheritance go from chromosome, to gene, to allele

false

True or False: at the end of meiosis II, each cell has more genetic information than the original cell at the start of meiosis I.

false

Meiosis ____ the number of chromosomes in a person's body cells to create _____ gametes.

halves / haploid

Diploid

having two copies of every chromosome

Recombination and independent assortment ____________ the amount of genetic diversity seen among haploid sperm and egg cells.

increases

What is a mutated proto-oncogene called?

oncogene

The difference in the proteins produced by a normal allele and a mutated allele is:

shape

True or False: A person with a hereditary mutation in a tumor suppressor gene would especially benefit from reducing their risk of cancer from environmental factors.

true

At the start of meiosis, each homologous pair of chromosomes consists of _____.

two chromosomes made of two sister chromatids each