BIO UNIT 4 Flashcards
How does the body make sex cells?
A body cell (46 chromosomes) goes through meiosis, resulting in a sex cell (23 chromosomes)
Body cell
-46 chromosomes
-Diploid (2n)
Sex cell (gamete) - amount of chromosomes and Haploid/Diploid
-23 chromosomes
-Haploid (n)
What are the sex cells in males/females?
-Male= sperm cells
-Female = egg cells
SPERM + EGG = Fertilization = Offspring
Male sex cell production
1 Body cell becomes 2 cells after MEIOSIS I. They become 4 SPERM CELLS after MEIOSIS II
What are the autosomal chromosomes?
-The first 22 pairs
Which pair is the sex chromosomes?
-Last pair
XX= Female
XY= Male
Where is the source of variation seen?
IN MEIOSIS
Crossing over
-During pairing of first division, chromosomes can exchange parts
Female sex cell production
1 Body cell becomes 2 cells after MEIOSIS I. After MEIOSIS II there is ONE EGG and 3 POLAR BODIES.
Mitosis vs Meiosis
Meiosis = sex cell formation = VARIATION!!
Mitosis = Body cell formation = NO VARIATION
Types of nondisjunction (failure to separate)
- Failure of a pair of homologous chromosomes to separate in Meiosis 1
- Failure of sister chromatids to separate during Meiosis 2
- Failure of sister chromatids to separate during mitosis
ANEUPLOIDY
Seen in daughter cells with abnormal chromosome numbers
An example of a monosomy
-Turners syndrome
-seen in females
-Results in short height, heart defects, etc.
Autosomal trisomy examples (3 copies of a chromosome)
- Downs syndrome (Trisomy 21)
-Edwards syndrome (trisomy 18)
-Patau syndrome (trisomy 13)
Sex chromosomes trisomy
-Klinefelter syndrome (XXY)
-XXY male
-Trisomy X (XXX)
Gametes pass along instructions/ DNA chromosomes which is….
HEREDITY
Who is the father of genetics?
-Gregor Mendel
-Argued that parents pass on heritable factors to their offspring
Gene
-Heritable factors that control a characteristic
Alleles code for a characteristic that can be passed from parent to offspring, aka….
A TRAIT
Different versions of a gene for the same trait (one from mom one from dad)
Allele
DOMINANT ALLELE
-The allele determining the organisms appearance
RECESSIVE ALLELE
-No noticeable effect in an organism
Law of Dominance
-A recessive allele can only be expressed when the organism has no dominant allele
Law of Segregation
-Each pair of alleles segregates during sex cell formation
Punnet square
-A chart that organizes genetic information (chart of probability)
Genotype
-Actual genetic makeup of an organism
-shows both alleles in gene pair
Homozygous genotype
Two alleles for a trait are identical
Heterozygous genotype
-Two alleles are not identical
Phenotype
-What the organism looks like
P generation
parents
F1 generation
First generation of offspring
F2
second generation of offspring from an F1 cross
What are the instructions for protein synthesis transferred to?
From DNA to RNA
Transcription
RIBOSOMES must make proteins SO…
1. DNA unzips at specific spot
- RNA polymerase matches a RNA nucleotide to a template strand
- Enzymes link nucleotides into a molecule of RNA
- mRNA leaves nucleus and travels to a ribosome in cytoplasm
mRNA processing: Step one
-5 prime cap is added:
-Modified guanine is added
-Helps protect mRNA from degradation
-Functions as an “attach here” sign for ribosomes
mRNA processing: Step two
-Poly (A) tail added:
- 50- 250 Adenines added
-Prevents degradation
-Helps ribosomes attach
-Facilitates the export of mRNA from the nucleus
mRNA processing: Step three
Rna splicing:
mRNA is edited so introns are cut out of the mRNA strand.
Exons
-Nucleotides that code for specific amino acids
Introns
“junk” - non coding nucleotides
Transcription steps
DNA > mRNA (exons and introns) > RNA processing > mRNA (exons, 5’ cap, poly (A) tail) > mRNA into cytoplasm
tRNA
-Special RNA molecules called Transfer RNA that amino acids link to
Translation
- mRNA travels to ribosome
- tRNA carries single amino acids to the ribosome
- tRNA with its anticodon binds to start codon on mRNA strand
- Ribosome moves along adding more amino acids to the protein through Elongation
- Stops at stop codon
- Protein is released
Anti- codon
- 3 base sequence on tRNA that links to a specific amino acid
Codon
- 3 base sequence on a mRNA that matches to a complementary tRNA anticodon
COVID Vaccine
vaccine = injection of mRNA
-mRNA translated into spike protein
-immune system learns what spike protein is and remembers
-upon infection, the virus is recognized and destroyed faster/stronger bc of previous vaccination
TWO TYPES OF MUTATIONS
POINT MUTATION - ONE nucleotide change.
FRAMESHIFT - INSERTION or DELETION of nucleotide
Causes shift to next codon
Why are mutations both good and bad?
GOOD - Can lead to genetic variability
BAD - Can cause diseases like cancer
GENE REGULATION
The turning on and off of genes
-Regulates portions
Gene regulation in eukaryotes
-More complex
CAN BE DONE AT:
-DNA level (shape/packaging)
-transcriptional level
-blocks mRNA
-degrades mRNA
EPIGENETICS
The turning on and off of genes because of environmental influences
Independent assortment
Chromosomes randomly line up = different combinations of chromosomes pairs
Difference between haploid and diploid
Haploid- 1 set of chromosomes
Diploid- 2 sets of chromosomes
What is a mutation?
An alteration of genetic code
What is a mutagen?
-An agent that causes mutations
-UV Rays from the sun
-X-Rays
-Chemicals found in things like cigarettes, pollution, etc.
What does RNA consist of?
SUGAR - Ribose
PHOSPHATE - PO4
BASES - A, G, C, U (A-U, G-C)
Turning off genes
Gene silencing
how do you regulate what genes are transcribed?
Gene regulation
Two main mechanisms of Gene Regulation
Chromosomal packaging
-Packing and folding of DNA controls access by RNA polymerase.
Regulate Transcription
-use non-coding RNA such as miRNA to block transcription
