Genetics Flashcards
What is DNA
-deoxyribonucleic acid
-the material that encodes all of the hereditary information in cells
-the eukaryotic cells it is contained in the nucleus (except during cell division)
What is RNA
-ribonucleic acid
-like a “photocopy” of a small section of DNA
-carried outside the nucleus to a ribosome and directs it to create specific proteins for the cell
What shape is DNA
a double helix consisting of two strands of repeating units called nucleotides
what is a nucleotide
a strand of repeating units
What are the parts of a nucleotide
each nucleotide consists of 3 parts
-a sugar
-a phosphate
-a base
How many types of nucleotides are there
4 types are possible because there are 4 different bases. The sugar and phosphate in each case is the same
what are hydrogen bonds
bases that extend towards each other that form weak bonds. Hydrogen bonds are the force that holds the two chains together
what are the complementary pairs
-Adenine + Thymine (A+T)
-Cytosine + Guanine (C+G)
what determines the specific information encoded by the gene
the number, type and order of the bases in the strand of DNA
What is DNA organized into
chromosomes
What are chromosomes
-long strands of DNA wrapped around a protein called a histone
-each chromosome contains information for hundreds of traits
what is a histone
a protein that a chromosome is wrapped around
what is a gene
a segment of a chromosome that codes for one particular trait
how does DNA duplicate
-hydrogen bonds break, the double helix “unzips”, exposing the bases
-free nucleotides that are floating in the nucleus then attach according to their complementary bases
-2 new, identical strands are formed from the original strand
Does DNA leave the nucleus
DNA is the master copy of genetic instructions, and so it does not leave the protection of the nucleus
What is a copy of DNA called
This copy is called RNA. When genetic instructions are needed for a cell to make a protein, a copy is made of the portion that encodes this information
what are the differences in DNA vs RNA
-RNA are also composed of nucleotides, but is single stranded and has differences in the nucleotides
-the sugar is called ribose instead of the deoxyribose found in DNA
-RNA is much shorter than DNA
-Thymine is replaced with a different base called uracil, which is still complementary to adenine
-RNA is free to leave the nucleus, while DNA is not
How does RNA work
-when DNA is unwound, the exposed bases act as a template to create a short strand of RNA that encodes information for one gene
-Once the RNA strand is complete it detaches from the DNA and the DNA rewinds
Why do some cells look and function differently
Each cell of your body contains all of the genetic information (DNA) to make a whole new you. However only certain genes are “turned on” in each cell, which is why skin cells look and function differently than stomach cells
What is mitosis
a type of cell division that creates identical cells
Why do cells undergo mitosis
-to create new cells for growth of the individual
-to replace dead or damaged tissues
What is a chromatid
each identical copy of the chromosome is known as a chromatid, and chromatids are attached by a small disk called a centromere
what is interphase
-most of a cell’s lifetime is spent in interphase
-the cell spends its time growing and making new materials
-at the end of interphase, before cell division occurs, the DNA is replicated, and the 2 copies are attached to each other.
what are the steps of mitosis
prophase, metaphase, anaphase, telophase
what is prophase
-chromatin condenses to form visible duplicated chromosomes
-nuclear membrane breaks down and the nucleolus disappears
-spindle fibers are formed from the centrosomes as they move to opposite poles of the cell. They are responsible for moving and organizing the chromosomes during cell division
what is metaphase
-spindle fibers move the chromosomes to the equator (center) of the cell by attaching to the centromere of the replicated chromosomes
what is anaphase
-the centromere splits apart and the sister chromatids are pulled to opposite poles by the shortening of the spindle fibers
what is telophase
-chromatids have reached the two opposite poles of the cells. Each of them is a single, non-replicated chromosome
-chromosomes begin to unwind and become less visible, and are now referred to as chromatin
-the spindle fibers break down and disappear, and the nuclear membrane reforms around the new set of chromosomes
what is cytokinesis
cytokinesis is the division of the cytoplasm to form 2 separate cells. It is sometimes considered part of telophase
how does cytokinesis work
an indentation forms along the middle of the cell membrane, and deepens until the cell pinches in 2. If it is a plant cell, a new cell plate forms between them. At the end of cytokinesis there are 2 genetically identical daughter cells
Why is the chromosome number often referred to in pairs
we inherit 2 copies of every trait, one from each parent
what are the sex chromosomes
the last pair of chromosomes that determine the sex of the child
what is the term for a chromosome that is not a sex chromosome
an autosome
what is a homologous chromosome
homologous chromosomes code for the exact same traits. one of the homologous pairs come from one parent, and one comes from the other parent
if you were looking at a picture of chromosomes under a microscope, how would you be able to tell if they were homologous
they are the same size, have their centromeres in the same location, and would have the same banding patterns when treated with stain
what is an allele
different forms of a gene
what is a karyotype and why might it be important
a photograph of all of the chromosomes of a cell. It allows doctors to detect if there are too many/ too few chromosomes in the cell
what does parent cell mean
the cell at the beginning of mitosis
what does daughter cell mean
cells at the end of mitosis
what is a somatic cell
body cells (any cells except for sex cells)
What are the stages of the cell cycle
interphase, mitosis, cytokinesis
what happens in the G1, S, and G2 phases of interphase
-G1 “gap 1”: growth
-S “synthesis”: replicates DNA
-G2 “gap 2”: preparing to divide
when do chromosomes become visible
not visible until prophase begins
what are the products of meiosis called
haploids
what re the two types of errors that can occur during meiosis
changes in chromosome structure, and changes in chromosome number
what causes errors in meiosis
crossing over and random assortment provide variation in the daughter cells of meiosis, but these processes also have the potential to cause chromosomal abnormalities
how do changes in chromosome structure happen
-during crossing over, the bonds holding the DNA together are broken and re-formed, but sometimes they do not re-form correctly.
-during crossing over, occasionally two chromosomes that are NOT homologous may exchange information
what are the four categories of errors that may result from improper chromosome structure
-Deletion: a piece of the chromosome is missing
-Duplication: a section of a chromosome is repeated 2 or more times in a row
-Inversion: a section of a chromosome is flipped
-Translocation: a portion of one chromosome becomes attached to a different chromosome
how do changes in chromosome number happen
when homologous chromosomes or sister chromatids fail to separate properly during meiosis (I or II), this is called non-disjunction. The result is a cell with too many chromosomes, or not enough chromosomes
what does non-disjunction mean
when homologous chromosomes or sister chromatids fail to separate during meiosis (I or II)
What is a trisomy
one extra chromosome
what is a monosomy
one too few chromosomes
what do trisomies and monosomies cause
usually result in the miscarriage of the fetus
what does genetics mean
genetics is the study of how traits are passed down from generation to generation
what is linkage
linked traits appear on the same pair of chromosomes, and therefore often cross over together
what is a genotype
letters used to represent the genetic makeup of the individual for a particular trait
what is a phenotype
describes the physical characteristic that results from the organisms genotype
what is a homozygous
organisms that have 2 identical alleles for a particular trait
what is heterozygous
organisms that have 2 different alleles for a particular trait
what are zygotes
fertilized eggs
what are assex-linked traits
traits that are found on the X chromosome but not on the Y
what are asholandric traits
traits found on the Y but not on the X chromosome. They can be passed only from fathers to sons
what is incomplete dominance
this describes a situation where neither allele completely masks the presence of the other, so “blending” of the alleles can occur
what is codominance
this describes a situation in which both alleles for a trait are expressed at the same time in a heterozygote (both are dominant)
what is selective breeding
the process of breeding plants and animals for desirable traits
what is artificial insemination
the process by which sperm are collected and concentrated before being introduced into the female’s reproductive system
what is in vitro fertilization
the technique used to fertilize cells outside the female’s body
what is cloning
a process that produces identical copies of genes, cells, or organisms
what is gene cloning
the use of DNA manipulation techniques to produce multiple copies of a single gene or segment of DNA
what are stem cells
an undifferentiated cell that can develop and become specialized into different cell types of the body
what are transgenic organisms
organisms whose genetic material includes DNA from a different species
