Unit 3: Genetic Continuity Section 1 Flashcards
What is DNA
-is a nucleic acid
-contains genetics that determine our inherited traits
-is a long molecule tightly wrapped into chromosomes
Structure of DNA
-shaped as a double helix (twisted ladder)
-“Steps of the ladder”~made of nitrogenous bases
-“Handles of the ladder”~made of a phosphate group attached to a ribose sugar called the sugar phosphate backbone
What are Nitrogenous bases
-Steps of DNA
-the 2 types are… Pyrimidines (Adenine (A) and Guanine (G)) and Purines Cytosine (C) and thymine (T)
Which nucleotides bind
-Adenine and thymine bind to create steps
-Guanine and cytosine bind to create steps
- the steps are called nucleotides
Structure of MRNA
-“m” stands for messenger
-is a nucleic acid made from the DNA molecule
-single helix
-has uracil instead of thymine
Making mRNA
-called transcription
What is translation
RNA—>Protein
After RNA is transcribed from DNA it can be used to make proteins that make physical
-tRNA brings in amunio acids that corespond with your starting nucleotides
What is replication
-making DNA
-process is semi-conservative because when a new double helix is made it consists of one of the old strands
Steps of Replication
- Initiation
-Dna unwinds using helicase, DNA unzips and hydrogen bonds are broken - Elongation
-DNA polymerase binds nucleotides to the strands of the unzipped DNA - Termination (proof-reading)
-Ligase corrects any mistakes in the replication and seals the DNA
What is Meiosis
-cell division in reproductive cells (egg and sperm)
-makes cells haploid so the zygote can have the correct amount of chromosomes
Chromosomes of sex cells
-they have 22 autosomes (non sex determining chromosomes)
-1 sex chromosome
-females have xx
-males have xy
Phases of meiosis 1
- Interphase
- Prophase
- Metaphase 1
- Anaphase 1
- Telophase 1
- Meiosis 2
Phases of meiosis 2
- Prophase 2
-centrioles replicate, no interphase - Metaphase 2
-centrioles to the poles, spindle fibres, chromosomes line up in the middle - Anaphase 2
-cleavage begins, centrioles shorten spindle fibres, chromosomes split at the centromere - Telophase 2
-cytokinesis, nucleus reforms around chromatids
-you now have 2 haploid cells
What is Down’s syndrome
-chromosomal disorder
-caused by trisomy of the 21st chromosome
-symptoms: short stature, developmental delays
Mitosis (what, steps)
-cell division of non sex cells
-Interphase: G1: cell grows, S: replication of chromosomes, G2: prep for mitosis, centrioles replicate
-Prophase: -Chromosomes shorten, nucleus dissapears
-metaphase: Centrioles to the poles, chromosomes line up in the middle, spindle fibres
-anaphase: cell elongates, chromatids are pulled apart
-telophase: Cytokinesis (cell splits), nucleus reforms, 2 cells are formed
Interphase (meiosis 1)
-first step
-chromosomes replicate
-centrioles replicate
-nucleus disappears
Prophase (meiosis 1)
-homologous chromosomes (similar) pair
-pairs make 4 sister chromatids (tetrads), this step is called crossing over
-Non-sister chromatids cross over each other and exchange segments of chromosomes
-crossing over allows for genetic variation 3
Metaphase (meiosis 1)
-centrioles to the poles
- spindle fibres attatch to homologous pairs
-pairs line up at the center randomly (random assortment) which allows for genetic variation
Anaphase (meiosis 1)
-homologous pairs are pulled to opposite poles
telophase (meiosis 1)
-cytokinesis
-both daughter cells are diploid with 2 copies of DNA
Turner’s syndrome
-monosomy of the X chromosome
-egg with no X chromosome is fertilized by a sperm with an X chromosome
-symptoms: female appearance, brown spots on body, poor development of secondary sex characteristics
Klinefelters syndrome
-Trisomy of sex chromosomes
-person inherits 2 x and 1 Y chromosome
Gametogenesis
-formation of sex cells during meiosis
Spermatogenesis
-spermatogonium undergo meiosis to be haploid
Oogenesis
-oocyte undergoes meiosis to create one haploid/viable ova and 3 polar bodies which aren’t viable
Abnormal meiosis (non-disjunction)
-mistake in meiosis
-non disjunction is when 2 homologous chromosomes move to the same poles
-this makes 1 daughter cell 2 chromosomes and 1daughter cell to be missing 1 chromosome
DNA and protein synthesis
-Happens in the cytoplasm
1.Transcription: Dna unwinds to create separate strands
-1 stand acts as a template for RNA synthesis
-complementary nucleotide is matched
2.Translation:mRNA leaves nucleus and attaches to the ribosome
3. Continued: tRNA attaches to the a- site of the ribosome, the p-site (to make room for another tRNA) and to create a link of amino acids, and the e-site where it will detach
-cycle repeats
Base pair substitution
-Changes the amunio acid
-swapping the nucleotide
Codons and anti-codons
Codons: the three letter codes in DNA
Anti-codons:the complementary 3 letter codes that tRNA introduces
Frameshift mutation
A deletion or insertion that leads to a shift in the DNA
