Mastering Biology - Ch 12, 13, 14 HW

X-linked dominant If the skin condition is caused by an X-linked dominant allele, a father would pass the allele on to all of his daughters, who would all have the skin condition. In contrast, the father would not pass the allele on to any of his sons because the sons would receive the father's Y chromosome, not his X chromosome. As a result, none of the sons would inherit the skin condition.

The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

Females would display this disorder with greater frequency than males. Men have only one X chromosome, whereas women have two. Thus, women have twice the chance of inheriting the dominant allele that causes this disorder. Remember that the disorder is caused by a dominant allele, so an individual who inherits a single dominant allele will display the disorder. Read about the inheritance of X-linked genes.

After replication is complete, the new DNAs, called ________ ___, are identical to each other.

During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a ___________ ____.

_______ _________ are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.

The enzyme that can replicate DNA is called ___ __________.

The new DNA strand that grows continuously in the 5' to 3' direction is called the _______ ______.

helicase: binds at the replication fork, breaks H-bonds between bases topoisomerase: binds ahead of the replication fork, breaks covalent bonds in DNA backbone single-strand binding protein: binds after the replication fork, prevents H-bonds between bases {At each replication fork, helicase moves along the parental DNA, separating the two strands by breaking the hydrogen bonds between the base pairs. (This makes the two parental DNA strands available to the DNA polymerases for replication.) As soon as the base pairs separate at the replication fork, single-strand binding proteins attach to the separated strands and prevent the parental strands from rejoining. As helicase separates the two parental strands, the parental DNA ahead of the replication fork becomes more tightly coiled. To relieve strain ahead of the replication fork, topoisomerase breaks a covalent bond in the sugar-phosphate backbone of one of the two parental strands. Breaking this bond allows the DNA to swivel around the corresponding bond in the other strand and relieves the strain caused by the unwinding of the DNA at the helicase.}

leading strand: daughter strand elongates toward replication fork, only one primer needed, made continuously lagging strand: made in segments, daughter strand elongates away from replication fork, multiple primers needed both strands: synthesized 5' to 3'

Step 1: A new fragment begins with DNA polymerase III binding to the 3' end of the most recently produced RNA primer, primer B in this case, which is closest to the replication fork. DNA pol III then adds DNA nucleotides in the 5' to 3' direction until it encounters the previous RNA primer, primer A. Step 2: DNA pol III falls off and is replaced by DNA pol I. Starting at the 5' end of primer A, DNA pol I removes each RNA nucleotide and replaces it with the corresponding DNA nucleotide. (DNA pol I adds the nucleotides to the 3' end of fragment B.) When it encounters the 5' end of fragment A, DNA pol I falls off, leaving a gap in the sugar-phosphate backbone between fragments A and B. Step 3: DNA ligase closes the gap between fragments A and B. These steps will be repeated as the replication fork opens up. Try to visualize primer C being produced to the right (closest to the replication fork). Fragment C would be synthesized and joined to fragment B following the steps described here.

Leading strand only: none Lagging strand only: DNA ligase Both leading and lagging strands: DNA polymerase III, single-strand binding protein, primase Neither leading nor lagging strand: telomerase

Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?

DNA replication complexes are grouped into factories, which are anchored to the nuclear matrix.

start/methionine: AUG stop codon: UAA, UAG, UGA amino acid: all others

"any technique that uses living organisms or their products to make or modify a product, to improve plants or animals, or to develop microorganisms for specific uses."

It starts after a certain nucleotide sequence called a promoter.

A __________ mutation leads to early termination of protein synthesis.

Protein synthesis ends when a stop _________ is produced.

A change in any triplet of bases in the mRNA sequence may or may not affect the coding of a(n)____ _____ and change the structure of the synthesized protein.

A silent mutation results in the insertion of the same amino acid as was coded for by the original nucleotide sequence.

Base substitution mutations alter a(n)nucleotide in the original DNA sequence.

A missense mutation can dramatically alter protein structure because it results in the insertion of a different amino acid than was coded for by the original nucleotide sequence.