Title [ Q1W6 ] GenBio Q1 Reviewer (1).pdf ✅

GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 6: ERRORS IN THE CELL CYCLE – PPT & lecture-based – 1.0 INTRODUCTION TO CELL ERRORS 1.1 RECALL : INTERPHASE CYCLE 1.2 BACKGROUND INFORMATION ● Over and over, small uncorrected errors are passed from the parent cell to the daughter cells. ● Cell cycle errors: refer to mistakes or abnormalities that occur during the various stages of the cell cycle (interphase, mitosis, meiosis, cytokinesis) ● These errors can have significant implications for the proper functioning and health of the cell, potentially leading to issues such as genetic mutations, cell death, or the development of diseases. Q: How does a cell normally correct those errors? Certain mechanisms instruct the cell to stop the cell cycle and repair the cell. 1.3 CODING & NON-CODING DNA ● There are two types of genetic material found in the genome, namely: a) Exons b) Junk DNA EXONS INTRONS Coding regions of the genome Non-coding regions of the genome (also called Junk DNA) Mutations or alterations can lead to changes in protein function, potentially resulting in genetic disorders or diseases. Mutations or alterations do not have an effect; Exists to mitigate mutations. 1.4 CANCER ● All cancers start with a gene mutation. ● Cancer: disease that has an abnormal growth in the cell / abnormal cell cycle ● Mutation: can be caused by (a) gene change, (b) addition, (c) removal. 2.0 TYPES OF GENES ● Cell cycle regulators ● Attributed to cause cancer when these genes become mutated. ● Two types: 2.1. Proto-oncogenes 2.2. Tumor-suppressor genes WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 1
GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 6: ERRORS IN THE CELL CYCLE 2.1 PROTO-ONCOGENES ● Positive cell cycle regulators - Genes that will tell the cell cycle that the output is successful ● When mutated, it becomes oncogenes. - Can cause cells to become cancerous. FUNCTIONS OF PROTO-ONCOGENES ● Stimulating cell division - Facilitates cell growth and proliferation. ● Inhibiting cell differentiation - Meaning, it hinders the process where cells change their specialized function. ● Preventing apoptosis (cell death). 2.2 TUMOR-SUPPRESSOR GENES ● Negative regulator protein - Prevent the cell from undergoing uncontrolled cell division. ● When there are too many errors, it can instruct the cell to die on its own (apoptosis). - Apoptosis: process of programmed cell death ● When mutated, errors can continue to multiply, leading to cancer. ● Two examples of tumor-suppressor genes: 2.2.1. BRCA1 & BRCA 2 2.2.2. P53 Gene 2.2.1 BRCA1 & BRCA 2 MUTATIONS ● BRCA Gene 1: Chromosome 17 ● BRCA Gene 2: Chromosome 13 ● When mutated, can lead to: a) Breast Cancer b) Ovarian Cancer c) Prostate Cancer d) Pancreas Cancer ● Pap smear: annual health check up to determine abnormalities around breasts. 2.2.2 P53 GENE ● Tumor suppressor protein that regulates cell growth and prevents cancer. WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 2
GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 6: ERRORS IN THE CELL CYCLE ● Functional p53 will deem the cell unsalvageable and trigger programmed cell death (apoptosis). ● A cell with a faulty p53 may fail to detect errors present in the genomic DNA. ● The damaged version of p53 found in cancer cells cannot trigger apoptosis. 3.0 CHROMOSOMAL ABERRATIONS ● Two main causes of chromosomal aberrations: a) Nondisjunction in meiosis b) Inability of the spindle fiber to attract the chromosomes ● Two basis of chromosomal aberrations: 3.1. Based on Structure 3.2. Based on Chromosomal Number NONDISJUNCTION IN CHROMOSOMES ● Occurs when homologous chromosomes/sister chromatids fail to separate to the opposite poles during meiosis, resulting in cells with gametes that are with the wrong chromosome complement. ● Can occur during: a) anaphase I (homologs) b) anaphase II (sister chromatids) 3.1 BASED ON STRUCTURE 3.2 BASED ON CHROMOSOMAL # ● Also called: Aneuploidy WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 3
GENERAL BIOLOGY I S.Y. ‘23 - ‘24 | S1Q1 | PPT AND LECTURE-BASED WEEK 6: ERRORS IN THE CELL CYCLE EUPLOIDY ANEUPLOIDY Normal state; organism possesses the correct # of chromosomes Changes in the number of chromosomes 2n = 46 23 pairs of chromosomes Trisomy (having three copies of a chromosome) Monosomy (having only one copy of a chromosome) ● Six main examples: 3.2.1. Trisomy 21 / Down Syndrome 3.2.2. Trisomy 18 / Edward Syndrome 3.2.3. Trisomy 13 / Patau Syndrome 3.2.4. Monosomy X0 / Turner Syndrome 3.2.5. Trisomy 23 (XXY) / Klinefelter Syndrome 3.2.6. Trisomy 23 (XYY) / Jacob’s Syndrome 3.2.1 TRISOMY 21 / DOWN SYNDROME ● 47 chromosomes ● Extra copy of C21 ● Affects both males & females ● Highest survival rate ● Typically present from birth and lasts throughout a person’s life. - Not specific to any particular age group. ● Characteristics: - Slanting upward eyes - Small ears, possibly folding slightly at the top - Small mouth, making the tongue appear large - Short neck - Common birth defects, including heart issues - Learning problems often present 3.2.2 TRISOMY 18 / EDWARD SYNDROME ● 47 chromosomes ● Extra copy of C18 ● Affects both males & more commonly in females ● Present from birth - Often leads to severe medical complications - Many affected individuals do not survive beyond infancy or early childhood. ● Characteristics: - Small, abnormally shaped head - Small jaw - Clenched fists - Overlapping fingers 3.2.3 TRISOMY 13 / PATAU SYNDROME ● 47 chromosomes ● Extra copy of C13 ● Affects both males & females at all ages ● Rarest and lowest survival rate ● Typically detected prenatally or shortly after birth ● Characteristics: - Polydactyly (extra fingers/toes) - Holoprosencephaly (failure to create double lobes of the cerebral hemisphere) - Facial clefting - Heart ailments 3.2.4 MONOSOMY X0 / TURNER SYNDROME ● 45 chromosomes ● Absence of one X sex chromosome ● Affects only females (sex-linked) ● Present from birth into adulthood ● Characteristics: - Wide neck WONRIKA ON TWT (X) | PPT | LECTURE | CAMPBELL BIO 8TH ED. GBIO SEM1 Q1 REVIEWER PAGE 4