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How does meiosis account for Mendel's concepts of segregation and independent assortment?
During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment, of homologous chromosomes is random.
Explain why sex-linked disorders are more common in males.
Since males only have one X chromosome, they are more likely to be affected
What is a barr body?
A dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome.
What is the recombinant frequency associated with genes on different chromosomes?
The recombinant frequency associated with genes on different chromosomes is 50% because they assort independently and are "unlinked"
How is the recombinant frequency determined?
The # of recombinant offspring / total # of offspring x 100%
Deletion mutation (chromosomal)
a type of mutation that involves the loss of one or more nucleotides from a segment of DNA.
Duplication mutation (chromosomal)
a genetic change where a section of a chromosome is abnormally copied, resulting in an extra copy of that genetic material
Inversion mutation (chromosomal)
occurs when a segment breaks off and reattaches within the same chromosome, but in reverse orientation
Translocation mutation (chromosomal)
a genetic change where a piece of one chromosome breaks off and attaches to a different chromosome, essentially swapping genetic material
What is epigenetic inheritance?
the transmission of traits from parents to offspring through changes in gene expression, not alterations in the DNA sequence itself, meaning that environmental factors can influence which genes are active or inactive
What are extranuclear genes? Where are they found? Are they inherited from mom or dad?
- refers to the transmission of genes occuring outside the nucleus
- found in most eukaryotes and (cytoplasmic organelles such as mitochondria and chloroplasts)
- Maternal influence
Name the scientists response for the DNA double-helix model.
James Watson and Francis Crick
Describe the experiments and scientific contributions made by Fredrick Griffith
- Two strains of a bacterium- Pathogenic (S cells)- Harmless (R cells)
- Evidence that DNA can transform bacteria
Describe the experiments and scientific contributions made by Avery, Carty, and MacLeod
- identified DNA as the "transforming principle" by isolating and purifying a substance from Streptococcus pneumoniae bacteria
- Inactivated: DNA, RNA, or Protein
- Checked for transformation
- Proved DNA must be genetic information
Describe the experiments and scientific contributions made by Hershey and Chase
- definitively proved DNA, not protein, is the genetic material
- - Studies of viruses that infect bacteria
• Bacteriophages (or phages)
Describe the experiments and scientific contributions made by Chargaff
- DNA composition varies among species
- Equal number of A and T bases
- Equal number of G and C bases
- evidence of diversity made DNA a more
credible candidate for the genetic material
Describe the experiments and scientific contributions made by Wilkinsand Franklin
- X-ray crystallography to study molecularstructure
- provided crucial information about the molecule's helical shape
- double helix model
Describe the experiments and scientific contributions made by Meselson and Stahl
- definitively proved DNA replicates in a semi-conservative manner
- incorporated non-radioactive isotopes of nitrogen with different weights into the DNA of E. coli
Describe the details of DNA structure.
made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix
What is the basic structure of a purine (adenine and guanine)?
have a two-ringed structure consisting of a nine-membered molecule with four nitrogen atom
What is the basic structure of a Pyrimidine (cytosine, uracil, and thymine)?
only have one single ring, which has just six members and two nitrogen atoms
What direction is DNA synthesized on the leading strand and lagging strand?
5' to 3' direction
What direction is the DNA template strand "read"?
3' to 5' direction
What end (5' or 3') of the newly added nucleotide is thenext nucleotide added to?
3' end
Why is an RNA primer needed in DNA replication?
provide the initiation sequence necessary for DNA polymerase to synthesize new strands
What role does complementary base pairing play in the replication of DNA?
allows DNA to accurately replicate itself
What is the precursor to a nucleotide?
a nucleoside; a nitrogenous base (like adenine, thymine, cytosine, or guanine) linked to a sugar molecule (ribose or deoxyribose
What causes damage to DNA?
- Chemicals
- Radioactive emissions
- X-rays
- Certain carcinogens (e.g. cigarette smoke)
- UV light
How can DNA damage be repaired?
- Mismatch repair
- Nucleotide excision repair
What is the purpose of telomeres? Why are telomeres important even though they do not encode for any genes?
- are protective caps found at the ends of chromosomes to prevent the loss of genes
- allow cells to divide without losing genes
How do gametes get "enough" DNA?
by undergoing meiosis
Describe the central dogma of molecular biology.
a theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein
Describe the central dogma as it relates to prokaryotes and eukaryotes?
Prokaryotes
-mRNA is immediately translated without more processing
- have simultaneous transcription and translation (cytoplasm)
Eukaryotes
- Nuclear envelope separates transcription from translation
- transcription in the nucleus
- translation in the cytoplasm
- RNA is processed before being used
Describe the flow of information from DNA to protein.
information encoded in DNA flows into RNA via transcription and ultimately to proteins via translation
How many codons encode for amino acids? Stop codons?
- 61 encode for amino acids
- 3 stop codons
What is meant by start codon?
the first base in a gene where the process of protein translation begins
- AUG
What are the stages of transcription?
initiation, elongation, and termination
What are the stages of translation?
initiation, elongation, termination
What are the different kinds of RNA?
mRNA, tRNA, rRNA
What "equipment" is used in RNA splicing?
RNA splicing carried out by ribozymes
How is a spliceosome formed?
- combo of snRNP's and other proteins
Small nuclear RNA (snRNA) molecules bind to specific proteins to form a small nuclear ribonucleo protein complex (snRNP), which combines with other snRNPs to form a large ribonucleo protein complex
Why is alternative RNA splicing important?
- It contributes to protein diversity and cellular adaptability. Number proteins an organism can produce is much greater than its number of genes
What enzyme "charges" a tRNA? Describe the process. How many different kinds of these enzymes are in the cell? Why?
aminoacyl-tRNA synthetase; This enzyme attaches the correct amino acid to its corresponding tRNA molecule, essentially "loading" the tRNA with the appropriate amino acid, ready to be used in protein synthesis at the ribosome.
What is the purpose of a chaperone?
a protein that assists other proteins in folding into their correct shape, preventing them from misfolding and aggregating
How can a polypeptide be modified before it becomes a fully functional protein?
Polypeptide chains undergo some modifications before they become fully functional. Some of these modifications include: proteolytic cleavage, lipidation and glycosylation
How does a ribosome begin attachment to the endoplasmic reticulum? Why does it attach to the ER?
when a specific sequence of amino acids, called a "signal peptide", is produced at the start of a growing polypeptide chain during protein synthesis
Silent Mutation
a genetic change in DNA that has no observable effect on the resulting protein because it alters the nucleotide sequence but does not change the amino acid sequence
Missense Mutation
alter the gross structure and folding of the protein (base-pair)
Nonsense Mutation
substitution of wrong nucleotide into DNA that produces an early stop codon
Frameshift Mutation
mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide
Which mutation(s) would be the least harmful to the cell? Which mutation(s) would potentially be the most detrimental?
Least harmful- silent point mutation
Most harmful- frameshift (insertions/deletions)
Be sure to be able to go from DNA to RNA and construct an amino acid chain using the codon table.
DNA sequence: ATGATGCATCGTAC
RNA sequence (transcription): UACUACGUGCAUG
Amino acid sequence: Tyr - Thr - Val - Met
What is epigenetic inheritance?
the passing down of traits from parents to offspring not through changes in the DNA sequence itself, but through modifications to the DNA that affect how genes are expressed
A white-eyed female fly is mated with a red-eyed male. What phenotypes, genotypes, and sexes will be observed in the F1 and F2 offspring?
Phenotypes- females would be red eye color, and males would be white eye color
Genotypes- w+w+, w
Sexes F1 generation- white eyed males while the female offspring had red eyes
Sexes F2 generation- 50% red-eyed females, 25% red-eyed males, and 25% white-eyed males, with no white-eyed females.
Dr. M has a tortoise-shell cat named Squirt. Why does she have a tortoise-shell coat? If a paternal X-chromosome is inactivated in one cell does that mean ALL cells will inactivate the paternal X-chromosome?
because the genes responsible for fur color are located on the X chromosome
