Science Exam Revision Semester 1 -DNA & Genetics

What is the structure of DNA?

DNA is structured as a double helix, resembling a twisted ladder.

What are the building blocks of DNA?

Nucleotides, which consist of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

What forms the sugar-phosphate backbone of DNA?

The sides of the DNA ladder are formed by alternating sugar and phosphate groups.

How many strands does DNA consist of?

DNA consists of two strands that are antiparallel.

What are the complementary base pairs in DNA?

Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

If a DNA sample has 20% Adenine, what are the percentages of the other bases?

It will have 20% Thymine, 30% Cytosine, and 30% Guanine.

How can you determine the sequence of a complementary DNA strand?

By using the base pairing rules: A with T, and C with G.

What are chromosomes?

Structures within cells that contain DNA, located in the nucleus of eukaryotic cells.

What is the relationship between DNA, genes, and chromosomes?

DNA carries genetic information, genes are segments of DNA coding for traits, and chromosomes are made of DNA containing many genes.

Which cells in the body contain genetic information?

Most cells contain genetic information in the form of chromosomes, except red blood cells in mammals.

What is a DNA mutation?

A change in the DNA sequence caused by factors such as radiation, chemicals, or errors during replication.

What is mitosis?

Cell division that results in two identical daughter cells, important for growth and repair.

What is meiosis?

Cell division that results in four genetically different daughter cells (gametes), important for sexual reproduction.

What are the stages of mitosis?

Prophase, metaphase, anaphase, telophase.

What are the stages of meiosis?

Prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, telophase II.

When does mitosis occur?

During growth, repair, and asexual reproduction.

When does meiosis occur?

During the formation of gametes (sperm and egg cells) for sexual reproduction.

How many daughter cells does mitosis produce?

Two daughter cells.

How many daughter cells does meiosis produce?

Four daughter cells.

What is a diploid cell?

A cell containing two sets of chromosomes (2n), most somatic cells are diploid.

What is a haploid cell?

A cell containing one set of chromosomes (n), such as gametes.

How is sex determined in humans?

By the X and Y chromosomes; females have XX and males have XY.

How are chromosomes inherited?

An equal number of chromosomes is passed on from each parent to offspring.

What are the types of allele combinations?

Homozygous recessive (rr), homozygous dominant (RR), and heterozygous (Rr).

What is dominant/recessive inheritance?

One allele masks the effect of the other.

What is incomplete/co-dominant inheritance?

Neither allele is completely dominant, resulting in a blended (incomplete) or shared (co-dominant) phenotype.

What is the purpose of a Punnett square?

To predict the genotypes and phenotypes of offspring from different parental genotypes.

What are the predicted genotypes from a Punnett square for two heterozygous parents (Rr)?

RR (25%): Homozygous dominant, Rr (50%): Heterozygous, rr (25%): Homozygous recessive.

What defines a carrier of a disease?

An individual who has one copy of a recessive allele for a disease but does not express the disease phenotype due to a dominant, non-disease allele.

How do the X and Y chromosomes differ?

The X chromosome is larger and contains more genes than the Y chromosome, which primarily contains genes related to male sex determination.

What is a karyotype?

A display of an individual's chromosomes, arranged by size and shape, used to identify chromosomal abnormalities.

What is Down syndrome and its chromosomal cause?

Down syndrome (Trisomy 21) is caused by an extra copy of chromosome 21.

What characterizes Turner syndrome?

Turner syndrome (XO) occurs in females with only one X chromosome.

What is Klinefelter syndrome?

Klinefelter syndrome (XXY) is a condition in males with an extra X chromosome.

What are sex-linked disorders and how are they inherited?

Sex-linked disorders, such as hemophilia or color blindness, are typically carried on the X chromosome.

What is the purpose of pedigree analysis?

To interpret a pedigree chart to determine the genotypes and phenotypes of individuals and identify carriers of specific traits or diseases.

What is the difference between weather and climate?

Weather refers to short-term atmospheric conditions at a specific time and place, while climate is the long-term average of weather conditions in a region.

What is global warming?

The increase in Earth's average surface temperature due to the rise in greenhouse gases in the atmosphere.

What are some impacts of global warming and climate change?

Rising sea levels, more frequent and intense heatwaves, changes in precipitation patterns, increased ocean acidification, and disruptions to ecosystems and biodiversity.

What is the Greenhouse Effect?

The natural process by which certain gases in the atmosphere trap heat, keeping the Earth warm enough to support life.

What is the Enhanced Greenhouse Effect?

The increase in the concentration of greenhouse gases due to human activities, leading to increased warming.

What are the roles of Crime Scene Unit (CSU) specialists?

Crime Scene Investigators document and collect evidence, Forensic Scientists analyze evidence in the lab, Photographers document the scene, and Evidence Technicians manage and preserve evidence.

What are the different CSU search methods?

Grid search, Spiral search, Quadrant or zone search, and Line search.

What is the difference between physical and trace evidence?

Physical evidence consists of tangible objects (e.g., weapons, documents), while trace evidence includes small, often microscopic evidence (e.g., hair, fibers).

How are fingerprints collected?

Fingerprints are collected using methods that vary by surface, such as dusting and lifting for smooth surfaces or chemical treatments for porous surfaces.

What is Algor Mortis?

The cooling of the body at a predictable rate after death, approximately 1.5°C per hour until it reaches ambient temperature.

How can the presence of bacteria help determine the time of death?

Bacteria in the body begin to decompose tissues after death, providing clues about the time elapsed since death.

What role do insects play in forensic science?

Insect life cycles can help estimate the time of death through forensic entomology.

What can blood spatter patterns indicate?

Blood spatter patterns can indicate the type of weapon used, the direction of impact, and the position of the victim and perpetrator.

What is the difference between ante-mortem and post-mortem?

Ante-mortem occurs before death, while post-mortem occurs after death.

What is an autopsy?

A post-mortem examination to determine the cause of death.

Who performs autopsies?

Pathologists perform autopsies.

What do toxicologists analyze?

Toxicologists analyze body fluids and tissues for the presence of drugs or poisons.

What is rigor mortis?

The stiffening of muscles after death due to the depletion of ATP, starting a few hours after death, peaking around 12 hours, and disappearing after 36-48 hours.

What are autoradiograms used for?

Autoradiograms are used in DNA fingerprinting to match a suspect's DNA to evidence from a crime scene.

What are the main components of an atom?

An atom consists of a nucleus and electrons, with the nucleus containing protons and neutrons.

What is the charge of protons, neutrons, and electrons?

Protons have a +1 charge, neutrons have no charge (0), and electrons have a -1 charge.

What is the atomic number?

The atomic number is the number of protons in the nucleus of an atom, determining the element's identity.

What is an ion?

An ion is an atom that has gained or lost electrons, resulting in a net charge.

What are cations and anions?

Cations are positive ions that have lost electrons, while anions are negative ions that have gained electrons.

How do atoms achieve a stable outer shell?

Atoms tend to gain or lose electrons to achieve a full outer shell, typically 8 electrons (2 for hydrogen).

What does the period number in the periodic table indicate?

The period number corresponds to the number of electron shells in an atom.

What does the group number in the periodic table indicate?

The group number corresponds to the number of outer shell electrons for main group elements.

What are the key characteristics of alkali metals?

Alkali metals (Group 1) are highly reactive and form +1 ions.

What are the key characteristics of alkaline earth metals?

Alkaline earth metals (Group 2) are reactive and form +2 ions.

What are the key characteristics of halogens?

Halogens (Group 17) are highly reactive nonmetals that form -1 ions.

What are the key characteristics of noble gases?

Noble gases (Group 18) are inert (unreactive) and have a full outer electron shell.

What is an independent variable in an experiment?

The independent variable is the variable that is manipulated or changed by the researcher.

What is a dependent variable in an experiment?

The dependent variable is the variable that is measured or observed in response to changes in the independent variable.

What is a hypothesis?

A hypothesis is a testable prediction or explanation of the relationship between two or more variables.

What are random errors?

Random errors are unpredictable errors that affect the precision of measurements and can be minimized by taking multiple measurements and calculating an average.

What are systematic errors?

Systematic errors are consistent errors that affect the accuracy of measurements and can be minimized by calibrating instruments and using control groups.

What should a conclusion in an experiment summarize?

A conclusion summarizes the findings of the experiment and states whether the hypothesis was supported or rejected.

What are the key components of graphing data?

Key components include a title, clearly labeled axes with appropriate units, and a line of best fit to represent the trend in the data.