Unit 3 Flashcards
Steps of Meiosis
- Synapsis
- Recombination
- Independent Assortment
- Reduction-Division
Steps of Cell Cycle
Interphase (G1, S, G2) Mitosis - Prophase - Metaphase - Anaphase - Telophase Cytokinesis
Protein
A macromolecule made up of repeating subunits known as amino acids, which determine the shape and function of the protein
Amino Acid
The building blocks of proteins. There are 20 different amino acids
Gene
A sequence of DNA that contains the information to make at least one protein
Gene Expression
The process of using DNA instructions to make proteins
Alleles
Alternative versions of the same gene that have different nucleotide sequences
Transgenic
Refers to organism that carries one or more genes from a different species
Regulatory Sequence
The part of a gene that determines the timing, amount, and location of protein production
Coding Sequence
The part of a gene that specifies the amino acid sequence of a protein. Coding sequences determine the identity, shape, and function of proteins; and it is the part of the gene that gets transcribed
Genetic Engineering
The process of assembling new genes with novel combinations of regulatory and coding sequences
Recombitant Gene
A genetically engineered gene
Transcription
1st stage of gene expression; cells produce molecules of mRNA from instructions encoded in genes in DNA
mRNA
The RNA copy of an original DNA sequence made during transcription
Translation
2nd stage of gene expression; mRNA sequences are used to assemble the corresponding amino acids to make a protein
RNA polymerase
The enzyme that carries out transcription. Copies a strand of DNA into complementary strand of mRNA
Ribosome
The cellular machinery that assembles proteins during translation
Codon
A sequence of three mRNA nucleotides that specifies a particular amino acid
Transfer RNA (tRNA)
A type of RNA that transports amino acids to the ribosome during translation
Anticodon
The part of a tRNA molecule that binds to a complementary mRNA codon
Genetic Code
The set rules relating particular mRNA codons to particular amino acids
How does a protein achieve its final 3D shape?
By having the correct sequence of amino acids for it to fold properly
What determines the correct sequence of amino acids?
The DNA sequence in a gene
How do differences in alleles result in different proteins?
A “misspelling” occurs and does not express the nucleotide sequence correctly which gives different instructions for proteins which results in abnormal or even non-functional proteins
Explain Gene Expression
DNA is copied into the mRNA sequence through transcription
The mRNA then gets fed into a ribosome to be translated into sequences that proteins
Explain process of transcription
- Enzyme RNA polymerase binds to the regulatory sequence and then copies the code from the DNA
- DNA-mRNA base pair rules G-C/A-U/T-A
- The mRNA transcript then exits the nucleus
Explain process of translation
- mRNA arrives in the cytoplasm; ribosome then “reads” each mRNA codons and brings in corresponding tRNA anticodons with amino acids attached.
- Ribosome then connects together each amino acid to form the protein chain
- Translation ends with a stop codon and then the protein folding occurs resulting in proper functional shape
How is a recombinant gene created?
A regulatory sequence from one gene is cut and pasted together with a coding sequence from another gene
Cancer
A disease of unregulated cell division: cells divide inappropriately and accumulate, in some instances forming a tumor
Cell Division
The process by which a cell reproduces itself; cell division is important for normal growth, development, and repair of an organism
Cell Cycle
The ordered sequences of stages that a cell progresses through in order to divide during its life
Stages: preparatory phases (G1, S, G2) and division phases (mitosis and cytokinesis)
Interphase
The stage of the cell cycle in which cells spend most of their time preparing for cell division
Three sub-phases: G1, S, G2
Mitosis
The segregation and separation of duplicated chromosomes during cell division
Cytokinesis
The physical division of a cell into two daughter cells
Sister Chromatids
The two identical DNA molecules that make up a duplicated chromosome following DNA replication
Mutation
A change in the nucleotide sequence of DNA
Cell Cycle Checkpoint
A cellular mechanism that ensures that each stage of the cell cycle is completed accurately
Apoptosis
Programmed cell death; cell suicide
Metastasis
The spread of cancer cells from one location in the body to another
Phases of Mitosis
Prophase, Metaphase, Anaphase, Telophase
Prophase
Replicated chromosomes begin to coil up; nuclear membranes disassemble; microtubule fibers form spindle (bulbs on end of diamond shape)
Metaphase
Microtubule spindles from opposite ends of cell attach to the sister chromatids of each chromosome and become aligned in the center of the cell
Anaphase
Microtubules shorten, pulling sister chromatids apart to the opposite ends of cell
Telophase
Identical sets of chromosomes reach each pole, microtubule spindles disassemble, nuclear membranes form around each set and form the daughter cell nuclei
Why do cells divide?
Embryonic development, cell replacement, wound healing
3 checkpoints in cell cycle
- G1-S (before DNA replication)
- right after S (check that DNA replication has been done correctly),
- during mitosis before chromatids separate) in normal cells during the process of cell cycle regulation.
Germ-Line Mutation
A mutation occurring in gametes; passed onto offspring
Somatic Mutation
A mutation that occurs in a body cell; not passed onto offspring
Mutagen
Any chemical or physical agent that can damage DNA by changing its nucleotide sequence
Carcinogen
A type of mutagen that causes cancer by damaging DNA
Proto-oncogene
“go” signal; A gene that codes for a protein that helps cells divide normally
Tumor-suppressor gene
“stop” cycle, A gene that codes for proteins that monitor and check cell cycle progression. When these genes mutate, the tumor suppressor proteins lose function
Oncogene
A mutated and overactive form of a proto-oncogene. Oncogenes drive cells to divide continually
Benign Tumor
A noncancerous tumor that will not spread throughout the body
Malignant Tumor
A cancerous tumor that spreads throughout the body
How do errors in DNA replication and repair result in mutations?
The wrong nucleotide is added during replication, causing mutations which causes a mismatch and the DNA is repaired incorrectly, making a new deformed allele
How does cancer develop?
Cancer is a genetic disease because it always involves mutations to cell cycle checkpoint proteins that results in a loss of control over the cell cycle. An accumulation of mutations can ultimately lead to cancer
How to reduce risk of cancer?
The types of cancer through heredity and random cell errors are unavoidable
But avoiding mutagens and carcinogens helps reduce risk of cancer from those chemicals
Why do people with “inherited” cancer often develop it relatively young?
Inherited mutations increase a person’s risk of developing cancer at an earlier age than normal. These individuals have inherited a predisposition for cancer to develop at an earlier age but they did not inherit cancer directly from a parent
Homologous Chromosomes
A pair of chromosomes that both contain the same genes. In a diploid cell, one chromosome is inherited from mother and one from father
Diploid
Having 2 copies of each chromosome
Haploid
Having only one copy of every chromosome
Gametes
Specialized reproductive cells that carry one copy of each chromosome. Sperms are male gametes and eggs are female
Meiosis
A specialized type of nuclear division that generates genetically unique haploid gametes
Zygote
A cell that is capable of developing into an adult organism. Formed when egg is fertilized by sperm
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
Independent Assortment
The principle that alleles of different genes are distributed independently of one another during meiosis
How many pairs of chromosomes are in human non-reproductive body cells?
46; 23 pairs
Why do almost all human chromosomes exist in homologous pairs?
One from each parent
how are the haploid cells created during the first division different from the haploid gametes that are produce during meiosis II?
he chromosomes are still replicated and paired with a sister at the end of meiosis I
Explain recombination during meiosis I
“cut and paste” exchange shuffles genetic information between one homologuos pair; pool noodle example
How does independent assortment contribute to the variation in the combination of chromosomes, genes, and alleles a child receives from their parents?
It shuffles the genetic information by the way that all of the maternal and paternal homologous pairs align randomly and then assort independently by segregation into two haploid cells
Difference between products of meiosis I and meiosis II
- 2 Haploid cells are produced at end of Meiosis I but the chromosomes are still replicated and paired with a sister
- 4 haploid gametes produced at end of meiosis II- and each is distinctly different
Law os segregation
When an organism produces gametes, the two alleles for any given trait separate so that each gamete receives only one allele. Offspring inherit only one of two alleles from each parent. They don’t blend but remain their own information passing from one generation to the next
Law of Independent Assortment
Two alleles for any given trait will segregate independently from any other alleles when passed on to gametes. Thus each gamete may acquire any possible allele combination and traits (sides of punnett diagram)
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; XX in females and XY in male
X-Linked Trait
A phenotype determined by an allele on an X chromosome
Incomplete Dominance
A form of inheritance in which heterozygotes have a phenotype that is intermediate between homozygous dominant and homozygous recessive
Codominance
A form of inheritance in which both alleles contribute equally to the phenotype
Continuous Variation
Variation in a population showing an unbroken range of phenotypes rather than discrete categories
Polygenic Trait
A trait whose phenotype is determined by the interaction among alleles of more than one gene
Multifactorial Inheritance
An interaction between genes and environment that contributes to a phenotype or trait
Aneuploidy Cells
An abnormal number of one or more chromosomes (either extra or missing copies)
Nondisjunction
The failure of chromosomes to separate accurately during cell division; nondisjunction in meiosis leads to aneuploid gametes
